Avatar won't ground

I have tried multiple solutions to ground my avatar (through a separate groundCheck and the Character Controller), but nothing seems to work.

The object has gravity (70) and there are no jump functions. I think there might be something wrong with the base code. Any tips or possible solutions are welcome. I have been stuck on this for so long.

// @FelienB paste code here instead

This is what the scene looks like:

Some scene info and what the scene looks like after playing and bumping into things, making the avatar fly.

(@FelienB write a question here) ?