Easiest and cheapest way to proceed is to change the brake light switch. Be sure to get a genuine MB one, most dealers only charge about $25. It does many different things and can trigger exactly the warnings you're getting.

Dealers will charge anywhere from $150 to $600 to diagnose and change it...ugh.

But were I you I'd swap it out and see if that takes care of it. If not then you can proceed down the rabbit hole...

Good luck.