ok, first off thx for the help and input, cause im not a car technician whatsoever

I think that the waterdrains indeed are blocked
I removed the cover, behind / underneath the glovebox compartement
There is a black box (with a sort of dynamo inside) underneath with a lid that you can remove
When i removed that lid it was filled with water and lots of remains of leafs, etc
I cleaned and it out and will pay a visit to my garage to follow up on the advice to remove the whippers, etc

I'll let you know what i will find there underneath