Question / Help Stream with 60fps but when play in the game the fps drop, and not stay 60fps

[arimited]

I have stream with x264 with I7-8700 and GTX1060 and everytime i stream PUBG my obs frame rate which is 60 ,always drop everytime i'm in the game.
but if i switch my screen back to the dekstop, the fps went back to 60fps and stay constantly.

I would like to know if my cpu or graphic card is broken? or my setting?