4 probleme with programation

hello

before start i try to explain you the most i work on the logo soft comfort V8.3 demo and this is for a test bench and to finish i already make a programe and this 4 probléme is my last probléme

i have 4  probleme

-my first  is i dont understand why i cant use comma to make calcul with the mathematique operatore and i need the coma to make my proggrame to write 49,9833 or just 49,983

-Block the value given by one sensor on screen when another sensor is activated on 1.

-Activate a heating resistor that reaches a requested temperature. (My issue is with connecting the heating resistor; I have already programmed the part related to raising the temperature.)

-After reaching a requested temperature, and at the requested temperature, increase the speed once again. (It is only the part of increasing the speed once again that is causing me a problem.)

thanks you if you can help me

I succeeded, no need for assistance, but now can you help me with my questions?,

thank you.