@yum - I solved the drop/reconnect issue. In Loop I just placed...
1.) Instead of: while (WiFi.status() != 3) you should rather write while (WiFi.status() != WL_CONNECTED) ... more readable, when you use the enums
2.) yes, yes, this would be the code for connecting or re-connecting, but the real problem is that the program is executing somewhere in your code and in my particular case it gets stuck at the line: if(client.connect(server, 443)) within ESP8266TelegramBOT.cpp. When there is an inadvertent cut of the WAP (no more WiFi) the program waits there (forever?) and you do not know that you would have to jump out and reconnect WiFi.
I am working on a solution with watchdog timer / timer interrupt to overcome this problem.