Help the permission problem? (Far Cry 4)

Help just a little on the topic, I have a screen resolution of 1280 x 1024, percent Athlon x3 460, 3.42 GHz RAM 8g, vidyuha Amd Radeon R7 240 2g Games such as MGS5, Mad max, Middle-earth Shadow of Mordor and Watch dogs work on my screen with 30-35 fps, and some like Far cry 4, Dead rising 3, Assassins Creed Unity, Gta 5 work with 15-18 fps, you make the resolution less, for example, 1024 x 768 from 35-60 fps, because of what detail can be the reason for this situation? Help pliz