Hey, I finally got a reply! Haha. What I did was add a menu for adjusting graphics such as render distance, pixel quality, etc. By default, everything is set to max which is why it was so hard for my computer to run it. After I made the graphics menu, I just turned down the settings and it seemed to work good.
I’m not sure if this is the case for you though since you said you can handle Grand Theft Auto V on maximum and you would think that would be able to handle your own game at max settings. Hopefully you get it fixed!