Nice one Glen, thank you for your comment, and I'm happy you found my video interesting!

There are quite a few abandoned buildings around Berlin that could be better used, instead of just sitting idle. But everything comes down to money. Most probably the building is listed, and therefore an investor will have his hands tied up with some 'jobsworth' from the local Council.
Usually in this case, the land owner will just leave the building to fall to bits. I'm not sure if the land here is privately owned, or state owned.

and yeah, the sigh at the beginning said "Forbidden" if my memory serves me right.
My German friends would say "If its forbidden, its fun"