The Error message was com.electronwill.nightconfig.core.io.ParsingException.notEnoughData
I know its because you use some other launcher but I use Minecraft Launcher and use forge for the mod. I even tried to reinstall forge but I can't figure out how to reinstall the Minecraft Launcher
crash-2020-04-29_14.57.06-client.txt

You can reinstall the launcher just by deleting the .minecraft folder (make a backup just in case), let the launcher download all of its files again. Then just install forge and try it again.

Duplicate of #256