Xperia Compact XZ2 touchscreen randomly dies while using

The phone is about 2 years old. I bought it used a year ago and for a few months now it sometimes randomly turns of its touchscreen, unrelated to what im doing. I then have to lock (power button) the phone and then unlock it again for it to work again. I already completely wiped and reinstalled the system. Any ideas what could cause this?

solution verification – How to proof this statement. “There are not odd integers x,y,z according to $(x-z)^2$ + $(y-z)^2$ = $(x+y)^2$.”

I did try to proof this by contradiction(I guess it works). So I suppose this statement is false but I have confused about the meaning of it.

If this statment is false it means “There are odd integers x,y,z according to $(x-z)^2$ + $(y-z)^2$ = $(x+y)^2$.” or “There are odd integers x,y,z according to $(x-z)^2$ + $(y-z)^2$ $neq$ $(x+y)^2$.” or…..

Is proof by contradiction a good method? and Could you help me how to do next from the statement that suppose to be false?

Thank you very much.