Buy a new phone

You're battery might got damage check your phone at service center

Here some things you can do to fix it ●Use power saving mode ●don't charge your phone above 85%● put all unnecessary apps into deep sleep.. only those apps you don't frequently use● update software & all apps from playstore & galaxy store

Due to 5G usage I guess

Ofcourse they show ads from long back even when the app name was game launcher