Hey Nomdan, that's a rendering issue. Wait, let me get you the guide.
If upgrading your video drivers does not fix the problem, you should consider switching video renderers, using the following steps.
- Hold down Shift while starting Ren'Py, or press Shift+G once Ren'Py has started.
- From the "Graphics Acceleration" menu that appears, choose the renderer to use.
- Choose "Quit", then restart Ren'Py.
https://www.renpy.org/doc/html/display_problems.html
This seemed to help other people with the same problem.
-Ex