Such ownership transfers occur frequently. Many owners sell once a property reaches a certain age and the risk of having to replace/invest in structural elements becoming expensive is elevating.

What do you know about the buyer and their investment/purchase motivation?

Are they an investor with no interest in living in your place, and only interested in maximising the return on their investment?

I echo the recommendation to join the Mieterverband, it may be more effective for support than here.