Use Full Screen on csgo setting. if that doesn't work, you should buy a better pc
  

I used some cardboard textures, but they stopped working a long time ago, you should look for a recent tutorial, to be able to go to better fps

buy better pc

i got 200 fps, and after the update over 300, maybe try to update your drivers? Or the easiest way... buy a new pc, i dont know alot about computers, but you could try to go in your launch options and enter this command: -novid -tickrate 128 -high +fps_max 0 -nojoy +r_dynamic 0 , hope it will work. :)

Yes, get a new pc.