Buying a house with a rented granny flat? New rental contract? More tips?

Good day,

I have bought a house with a rented granny flat ([Räumung/Übergabe und Zahlung ist erst in einigen Monaten]). The granny flat should continue to be rented out, at least for the next few years (at least 5). The tenant also wants to continue living there.
What are the advantages/disadvantages if I let the old rental agreement continue? Or is it advisable to draw up a new rental agreement?
Regardless of the "content" of the contract, it is also about termination periods, etc.
I do not want to increase the rent - maybe after a few years.
On the internet, I only find the rights of tenants. What is actually best for the landlord is not described.

Many thanks in advance

What are the advantages/disadvantages if I let the old rental contract continue? Or is it advisable to draw up a new rental contract?

You have absolutely no chance to draw up a new rental contract, because: purchase does not break rent! Exception: purchase through a compulsory auction. You therefore enter into the existing rental contract with all rights and obligations. Rhineland greetings

Thank you - that is "actually" clear to me so far.

However, if I tell the tenant that I would like to make a new lease agreement and they agree, that should be possible - right?

Currently, I assume that the tenant agrees - at least I had that impression during the viewing.

If I tell the tenant that I would like to make a new rental agreement and he agrees, that should be possible - right?

Theoretically yes. However, all associations advise against doing this. Maybe you should first probe your tenant more closely and then think about it.

What is supposedly so bad about the "old" rental agreement?

Rhineland greetings

Basically, nothing about the contract bothers me. That’s why I’m asking here. It could be that someone points out something that might be interesting for me as a landlord. How does it proceed if the contract stays? Do you then cross out the current owners’ names on the first page and replace them with our names?

that's why the tenant would be ill-advised. If there is a clause that is interesting for the landlord, there are many reasons to believe that it is uninteresting for the other party ;)

In my opinion, you don't have to do anything