Usually this is the result of the game thinking it's in a different resolution than it actually is. Try changing the resolution to something different and see if that fixes the problem.
Also, you can try deleting your settings file to reset everything to default. It can be found on your PC here: C:\Users\YourUserName\AppData\Local\ShopSim\Saved\SaveGames
If you're having trouble finding it, reading this post (and its replies) should help: https://itch.io/post/128793/view-in-topic