Set the PASSABLE flag for your entities and use IGNORE_PASSABLE in your c_move code.

In your walk code you have to trace down to the floor and so you can set your entity back to the floor. Search for c_trace in the manual.

Another question do you do already the workshop?

Thanks, IGNORE_PASSABLE worked!
I did the workshop from 0-25, but it was just the basics so I tried to learn more from the AUM magazine about c_trace but the codes with the movementsystems were to complicated so I tried to do my own system.

EDIT: I found another movement system with gravity in it...I'm going to change it to that.