Basement compartment door lock (house from 1578!) can no longer be opened

Does anyone have a tip for me or my son on how to open this basement compartment again? Until a few weeks ago, the key could still be turned, now it goes into the lock but can no longer be turned. Removing the lock or the hinges seems almost impossible, it has already been oiled, but unfortunately without success. My son doesn’t really want to bother the super nice landlady with it, nor call a locksmith for now, and also doesn’t want to use brute force. Does anyone have any other ideas?

The door should be able to be opened via the hinges (right). However, this entails a renewal. Is that wood? No, an axe will do as well.

Warranty? It can't be that the thing is broken after such a short time.

Raw force is not my first choice.

I would first spray W40 in and then try again by turning it counterclockwise first and then clockwise, possibly a bit more forcefully? If necessary, until the key breaks. You probably need a new lock anyway.

If that doesn't work, then cut off the screws of the door hinges with an angle grinder. Then the door will definitely open.

In my opinion, the landlord is not responsible for small repairs.

If the manual skills are limited, then one should have a professional do it. However, it should be commissioned by the landlord, because then it is no longer a small matter.

tadaa! It is open. But that was only possible by cutting off the screws of the hinges. And when you see the condition of the lock, it’s no wonder that nothing moved anymore. Now there is a new lock (new screws etc.) and everything is fine again. Thanks again to everyone for your help!