Hello @Nex-Leo and welcome to the community!
TouchGFX runs even when the screen is not changing because he needs to check if something has to change.
Multiple things happens, including a check every ticks (usually 60 times per second).
The handleTickEvent function is called, so make sure to keep the code inside of it as efficient as possible.
Perhaps you have some area of the screen that you invalidate even when nothing is changing, so make sure to optimize your invalidated area.
Finally, the MCU load can be drastically reduce by using a graphic accelerator such as NeoChrom or Chrom-ARTbut this is embedded inside your chip (which one are you using?).
Regards,