- The “7” trainer is for the Origin version of the game. (Link).
- The “11” trainer is for the Steam version of the game. (Link).
You need to make sure you are using the correct trainer for whatever version of the game you have. The Steam trainer won’t work on the Origin game and vice versa. If you have a cracked copy of the game then the chances are neither trainers will work.
Aside from that, I cannot see how a trainer can cause you to have visual glitches in the game. Because trainers do not touch the game in any way, they just alter memory addresses in the RAM of your PC. Nobody else has reported having the same issue as you here.
Make sure your GPU is up to date. You might find the solution to your screen issue on an official Mad Max game discussion community.