if heating too much your battery will become weak. when playing high graphics games phone will warm little bit that's okay, but heating too much is bad for your phone and ofcourse your battery capacity will reduce. contact Samsung let them know the issue and i hope they will help you.
sir, i don't know how much is your phone heating, playing game and watching online videos too long may your phone warm little that's ok, heating too much badly is not ok something problem with your phone or inside it's software's or maybe your phone dressing (case) make hard to cool. pls visit: https://www.google.com/amp/s/www.businessinsider.com/why-does-my-samsung-galaxy-s10-get-hot%3famp let the Samsung know the issue, if they already got the problem they know to solve it than as.