She's not going to have any leg to stand on in court if you get that far unless there's some explicit language prohibiting the owner from assigning responsibilities to another legally authorized party, and I'm guessing there isn't if another PM company was maintaining the lease and provisions - and the fact that the tenant was voluntarily working with the other PM confirms the acceptance of an authorized agent even if it's not explicitly stated, the same way if you accept rent from a tenant after a lease expires you imply acceptance of the lease terms continuing (which is why you should always have a holdover provision). 

I'm new here to the BiggerPockets site. I have 1 rental for which I have been renting since 2018. I am looking to purchase more rental properties in the near future.

Legal and Language BarriersWhile Germany has a transparent legal process, navigating the local real estate market can be challenging for American investors who are not familiar with German legal and tax systems.

Unless you negotiate a new contract or addendum with your PMC, they do NOT have to abide by any requests/demands you make that contradict what's written in the management contract.If they have in fact NOT followed the terms of their contract, then you'll want to send them something in writing pointing out the specific language in their contract that they violated and ask what they plan to do about it.If they fail to correct or address the issues, then you'll want to start looking for a new PMC.

It does seem to use a little bit of vague language I guess when it comes to "can it be easily/cheaply done".  

You can pretty much learn everything you need to know about S8 within 2-4 hours online!

Start here...have a solid lease with an Addendum of dealbreakers/rules that are written in plain everyday language. 

thethat is really weird language but the way I read that is if rent is $1550.

BTW there is a free trial and the Starter monthly plan is $119.It also allows you to search through consumer information such as property owner "credit worthiness," Credit card usage, buying power, age, language, family members in the house, and many other fields that are above and beyond property characteristics, which is unique.

You will have a leg up on the language, transactions, inspections etc.