Hello please excuse if this is a dumb question, but...
I moved into a new flat at the start of the year, but I have continually had problems with the pipes. First, when I had my washing machine installed, the technician said he did as much as he could but there was a part missing in the wall itself which prevented the full connection and he told me to contact me hausmeister for it. So I did, and the hausmeister added something to the wall, but then told the landlord (falsely) he had done the whole installation. Then, I had my kitchen sink installed, and again the technician said something is not right with the pipes in the wall, and so the sink water doesn't drain properly and the pipes leak. Meanwhile, the toilet has never flushed properly and it requires a plunger every single time. I have contacted my landlord, but the hausmeister has falsely said there is nothing wrong with the pipes.
Essentially, I have the word of 1 creepy hausmeister against 3 independently commission technicians/repairmen -- the independent ones all say only the hausmeister can fix it, and the hausmeister falsely says nothing is broken. I get the feeling the landlord is just trying to skimp on the cost of repairs, because it was similarly an uphill battle to get other damages fixed which occurred before I moved in
What can I do in this case? I haven't had a working sink or toilet in 2.5months and I'm really quite fed up. I would now rather pay an independent contractor to fix this ASAP for the sake of time, but I wonder if I can then bill my landlord for it? Surely, they would refuse paying it but legally what is my recourse? I really believe working pipes in the building is a basic minimum. If I go about the route of hiring someone else and then holding them accountable for the costs, what are the legal steps I would need to take to do so?