Walauweh...you are such an optimistic person. Such terrible mess and you still consider yourself lucky.
I salute you.

If you want to continue to stay in this unit, you really need to work closely with your upstairs neighbor to resolve it. Most likely water seepage problem from the walls.
You should also complain to the landlord and ask him/her to compensate you for your losses/damage and even rental reason being his/her unit is not fit for staying.