Q: imac 27 windows 10 problems

Hello! i purchased this Imac few weeks ago, and i am already seeing some problems. I installed Windows. First when i tried to open a game it usually turn out smaller than usual, second even if i drag to make it bigger, it text display on the computer will still be small. extremely hard to read! please help me out, should i reinstall the windows system or is there anything i can do about it. I'd also contact the Microsoft and according them that the video card in Imac 27 isn't compatible with windows 10.  any source or help would be grateful i would also screen shot some software. some of them are Chinese but just ignore it.

it suppose to be bigger to those who plays league

h=just everything smaller than usual