diff --git a/CMakeLists.txt b/CMakeLists.txt
index bd85bfe..d7dfcd6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,7 +5,7 @@ set(CMAKE_CXX_STANDARD 17)
 
 set(CMAKE_BUILD_TYPE Release) # manually set build type (Release / Debug)
 set(LIB_METHOD STATIC) #SHARED / STATIC
-set(PROJECT_VERSION 1.3.1-dev)
+set(PROJECT_VERSION 1.3.1)
 option(BUILD_DOC "Build documentation" ON)
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
@@ -69,7 +69,7 @@ add_library(logger ${LIB_METHOD}
 set(SOURCE
         src/main.cpp
         src/IPRefresher.cpp
-        src/Credentials.cpp)
+        src/Config.cpp)
 
 add_executable(iprefresher ${SOURCE})
 
diff --git a/README.md b/README.md
index 870b176..1d6aa64 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,16 @@
 # DynuIPRefresher
 A lightweight C++ application to setup a service for refreshing a dynamic IP to the Dynu servers. 
+Dynu.com is a free DDns service and provides an API.
+
+## Installation
+Download the latest Release at [Release_Page](https://github.com/Lukas-Heiligenbrunner/DynuIPRefresher/releases).
+I'm providing executables for Debian/Ubuntu (.deb) and RHEL/Debian (.rpm). 
+But you can still compile the code my your own (see build section).
+
+## Configuration
+There is a configuration file `/etc/iprefresher.cfg` where you have to specify the DYNU API key (get it from their homepage), the domainid and your domain.
+Furthermore, you can optionally specify a Telegram API key and a Chat ID if you want to be notfied when your local ip changes.
+
 
 ## Build
 ## Basic Build
diff --git a/config/iprefresher.cfg b/config/iprefresher.cfg
index cd5f136..e8a0dc5 100644
--- a/config/iprefresher.cfg
+++ b/config/iprefresher.cfg
@@ -9,4 +9,4 @@ domainname = ""
 
 ## Telegram API Config (optional)
 #telegramApiKey = ""
-#chatId =""
+#chatId = ""
diff --git a/inc/Credentials.h b/inc/Config.h
similarity index 94%
rename from inc/Credentials.h
rename to inc/Config.h
index db0acc5..1c9b728 100644
--- a/inc/Credentials.h
+++ b/inc/Config.h
@@ -6,7 +6,7 @@
 
 #include <string>
 
-class Credentials {
+class Config {
 public:
     static std::string dynuapikey;
 
diff --git a/inc/IPRefresher.h b/inc/IPRefresher.h
index c3e4b03..7220adf 100644
--- a/inc/IPRefresher.h
+++ b/inc/IPRefresher.h
@@ -11,6 +11,9 @@ public:
      */
     void checkIPAdress(bool force);
 
+    /**
+     * default constructor
+     */
     IPRefresher();
 
     /**
diff --git a/inc/Logger.h b/inc/Logger.h
index 9bfc56a..d486f93 100644
--- a/inc/Logger.h
+++ b/inc/Logger.h
@@ -15,8 +15,8 @@ public:
 
     static void log(const std::string &message, int level);
 
-    static const int Debug;
-    static const int Message;
-    static const int Warning;
-    static const int Error;
+    static const int Debug = 4;
+    static const int Message = 3;
+    static const int Warning = 2;
+    static const int Error = 1;
 };
diff --git a/inc/api/DynuAPI.h b/inc/api/DynuAPI.h
index c78148d..3d169fc 100644
--- a/inc/api/DynuAPI.h
+++ b/inc/api/DynuAPI.h
@@ -21,9 +21,9 @@ public:
      * @param domainId ID of domain received by Dynu
      * @param domainName domainname to refresh
      */
-    void init(std::string dynuApiKey, std::string domainId, std::string domainName);
+    void init(const std::string& dynuApiKey, const std::string& domainId, const std::string& domainName);
 private:
-    std::string dynuapikey;
+    std::string dynuapikey; // Dynu API key
 
     std::string domainid; //id of the dynu domain
     std::string domainname;
diff --git a/inc/api/Hashmap.h b/inc/api/Hashmap.h
index e55db89..96f4717 100644
--- a/inc/api/Hashmap.h
+++ b/inc/api/Hashmap.h
@@ -4,7 +4,6 @@
 
 #pragma once
 
-
 #include <iostream>
 #include <vector>
 
diff --git a/inc/api/TelegramAPI.h b/inc/api/TelegramAPI.h
index dc09035..5cdaaf0 100644
--- a/inc/api/TelegramAPI.h
+++ b/inc/api/TelegramAPI.h
@@ -14,7 +14,7 @@ public:
      * send telegram Message to predefined destination
      * @param text message
      */
-    void sendMessage(std::string text);
+    int sendMessage(const std::string& text);
 
     /**
      * init Telegram api with apikey and chatid
diff --git a/src/Credentials.cpp b/src/Config.cpp
similarity index 76%
rename from src/Credentials.cpp
rename to src/Config.cpp
index c1c124d..85bd460 100644
--- a/src/Credentials.cpp
+++ b/src/Config.cpp
@@ -2,20 +2,20 @@
 // Created by lukas on 11.02.20.
 //
 
-#include <Credentials.h>
+#include <Config.h>
 #include <iostream>
 #include <cstring>
 
 #include "libconfig.h++"
 
-std::string Credentials::dynuapikey;
-std::string Credentials::domainid; //id of the dynu domain
-std::string Credentials::domainname;
+std::string Config::dynuapikey;
+std::string Config::domainid; //id of the dynu domain
+std::string Config::domainname;
 
-std::string Credentials::telegramApiKey;
-std::string Credentials::chatId;
+std::string Config::telegramApiKey;
+std::string Config::chatId;
 
-bool Credentials::readCredentials() {
+bool Config::readCredentials() {
     libconfig::Config cfg;
     try {
         cfg.readFile("/etc/iprefresher.cfg");
@@ -40,7 +40,6 @@ bool Credentials::readCredentials() {
         // optional parameters
         telegramApiKey = (std::string) cfg.lookup("telegramApiKey");
         chatId = (std::string) cfg.lookup("chatId");
-        std::cout << "Store name: " << dynuapikey << std::endl;
     }
     catch (const libconfig::SettingNotFoundException &nfex) {
         // triggered if setting is missing in config
@@ -49,5 +48,5 @@ bool Credentials::readCredentials() {
         }
     }
     // check if needed values aren't empty
-    return !(Credentials::dynuapikey.empty() || Credentials::domainid.empty() || Credentials::domainname.empty());
+    return !(Config::dynuapikey.empty() || Config::domainid.empty() || Config::domainname.empty());
 }
diff --git a/src/IPRefresher.cpp b/src/IPRefresher.cpp
index c031ba6..d931fdd 100644
--- a/src/IPRefresher.cpp
+++ b/src/IPRefresher.cpp
@@ -14,7 +14,7 @@
 #include <Logger.h>
 
 #include <IPRefresher.h>
-#include <Credentials.h>
+#include <Config.h>
 
 void IPRefresher::checkIPAdress(bool force) {
     FileLogger logger;
@@ -34,11 +34,11 @@ void IPRefresher::checkIPAdress(bool force) {
             Logger::message("ip changed! -- from :" + oldip + "to: " + ip);
 
             DynuAPI dynu;
-            dynu.init(Credentials::dynuapikey, Credentials::domainid, Credentials::domainname);
+            dynu.init(Config::dynuapikey, Config::domainid, Config::domainname);
 
             if (dynu.refreshIp(ip)) {
                 TelegramAPI tele;
-                tele.init(Credentials::telegramApiKey, Credentials::chatId);
+                tele.init(Config::telegramApiKey, Config::chatId);
                 tele.sendMessage(oldip + " moved to " + ip);
             } else {
                 //error
@@ -53,14 +53,16 @@ void IPRefresher::checkIPAdress(bool force) {
 IPRefresher::IPRefresher() = default;
 
 IPRefresher::IPRefresher(bool loop) {
-    if (Credentials::readCredentials()) {
+    if (loop) {
         Logger::message("startup of service");
-        while (loop) {
-            Logger::message("starting check");
-            checkIPAdress(false);
-            std::this_thread::sleep_for(std::chrono::milliseconds(300000));
+        if (Config::readCredentials()) {
+            while (true) {
+                Logger::message("starting check");
+                checkIPAdress(false);
+                std::this_thread::sleep_for(std::chrono::milliseconds(300000));
+            }
+        } else {
+            std::cout << "incorrect credentials!" << std::endl;
         }
-    } else {
-        std::cout << "incorrect credentials!" << std::endl;
     }
 }
diff --git a/src/Logger.cpp b/src/Logger.cpp
index 5653cb3..6822bf0 100644
--- a/src/Logger.cpp
+++ b/src/Logger.cpp
@@ -7,12 +7,6 @@
 
 #include "Logger.h"
 
-
-const int Logger::Warning = 1;
-const int Logger::Debug = 2;
-const int Logger::Message = 3;
-const int Logger::Error = 4;
-
 void Logger::debug(const std::string message) {
     log(message, Logger::Debug);
 }
diff --git a/src/api/DynuAPI.cpp b/src/api/DynuAPI.cpp
index 89c5aff..e91bad4 100644
--- a/src/api/DynuAPI.cpp
+++ b/src/api/DynuAPI.cpp
@@ -5,19 +5,16 @@
 #include "api/DynuAPI.h"
 
 int DynuAPI::refreshIp(std:: string ip) {
-
     Hashmap<std::string, std::string> args;
     args.add("name", domainname);
     args.add("ipv4Address", ip);
 
     std::vector<std::string> headers;
-    headers.push_back("accept: application/json");
-    headers.push_back("User-Agent: Mozilla/5.0 (compatible; Rigor/1.0.0; http://rigor.com)");
-    headers.push_back("API-Key: " + dynuapikey);
+    headers.emplace_back("accept: application/json");
+    headers.emplace_back("User-Agent: Mozilla/5.0 (compatible; Rigor/1.0.0; http://rigor.com)");
+    headers.emplace_back("API-Key: " + dynuapikey);
 
-    std::string dynurepl = request("https://api.dynu.com/v2/dns/" + domainid, true, args, headers);
-
-//    std::cout << "[DEBUG] api reply:: " << dynurepl << std::endl;
+    const std::string dynurepl = request("https://api.dynu.com/v2/dns/" + domainid, true, args, headers);
 
     if (dynurepl != "{\"statusCode\":200}") {
         return -1;
@@ -26,7 +23,7 @@ int DynuAPI::refreshIp(std:: string ip) {
     }
 }
 
-void DynuAPI::init(std::string dynuApiKey, std::string domainId, std::string domainName) {
+void DynuAPI::init(const std::string& dynuApiKey, const std::string& domainId, const std::string& domainName) {
     this->dynuapikey=dynuApiKey;
     this->domainid=domainId;
     this->domainname=domainName;
diff --git a/src/api/TelegramAPI.cpp b/src/api/TelegramAPI.cpp
index f44d589..3df25ea 100644
--- a/src/api/TelegramAPI.cpp
+++ b/src/api/TelegramAPI.cpp
@@ -4,7 +4,9 @@
 
 #include "api/TelegramAPI.h"
 
-void TelegramAPI::sendMessage(std::string text) {
+#include <Logger.h>
+
+int TelegramAPI::sendMessage(const std::string& text) {
     Hashmap<std::string, std::string> args;
     args.add("chat_id", chatid);
     args.add("text", text);
@@ -12,10 +14,16 @@ void TelegramAPI::sendMessage(std::string text) {
     std::vector<std::string> headers;
 
     std::string reply = request("https://api.telegram.org/bot" + apikey + "/sendmessage", false, args, headers);
-//    std::cout << "[DEBUG] " << reply << std::endl;
+
+    unsigned const long ULONG_MAX = -1;
+    if (reply.find("\"error_code\"") != ULONG_MAX) {
+        Logger::error("failed to refresh the ip (Dynu API)");
+        return -1;
+    }
+    return 1;
 }
 
-void TelegramAPI::init(std::string apikey, std::string chatid) {
+void TelegramAPI::init(const std::string apikey, const std::string chatid) {
     this->apikey = apikey;
     this->chatid = chatid;
 }
diff --git a/src/main.cpp b/src/main.cpp
index 9c238be..3ef49ea 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,9 +1,16 @@
+//
+// Created by lukas on 18.06.19.
+//
+
 #include <iostream>
 #include <IPRefresher.h>
 #include <Version.h>
 #include <Logger.h>
-#include <Credentials.h>
+#include <Config.h>
 
+/**
+ * application entry point
+ */
 int main(int argc, char *argv[]) {
     if (argc > 1) {
         std::string firstarg(argv[1]);
@@ -17,7 +24,7 @@ int main(int argc, char *argv[]) {
             std::cout << "Version " << Version::VERSION << std::endl;
         } else if (firstarg == "-f" || firstarg == "--force") {
             IPRefresher ipr;
-            if (Credentials::readCredentials()) {
+            if (Config::readCredentials()) {
                 ipr.checkIPAdress(true);
             } else {
                 std::cout << "incorrect credentials!" << std::endl;
@@ -31,12 +38,11 @@ int main(int argc, char *argv[]) {
     } else {
         IPRefresher ipr;
         Logger::message("starting check");
-        if (Credentials::readCredentials()) {
+        if (Config::readCredentials()) {
             ipr.checkIPAdress(false);
         } else {
             std::cout << "incorrect credentials!" << std::endl;
         }
-
     }
 
     return 0;