Okay, after getting really desperate I asked a experienced user here called Pretzal and he went over it with me in full detail. And I now got it working again!I would share the solution but he told me that its a very risky procedure and could cause in a brick.. If you need help with a similar problem the best is to ask a experienced user
Would be interesting to know what worked. It goes without saying that trying to rebuild your Switch nand is a worst-case-scenario option that could leave you with a brick.
