Apartment and Sommer House have old owners but should be trasferred to a new e-mail address

My daughter-in-law has been managing my rented accommodations so far, but unfortunately she doesn't have any time for this anymore because she is very busy, so I would like to take over this task from her in the future.

I would like her to no longer be able to access and handle these, and these should be transferred to my e-mail address.

I would like your kind help in this. Please tell me what I need to do to achieve this.

Thank you very much.