What can I do about a landlord who refuses to maintain the heating?

A landlord who refuses to maintain the heating is violating their legal obligations, since you have the right to a decent home with functional heating. The first step is to send them a formal written notice (email or registered letter with proof of receipt), describing the problem precisely and giving them a reasonable timeframe to fix it, like 15-30 days. Keep a copy of everything you send - that's important for what comes next.

If the landlord ignores your request, you can contact the local town hall or housing inspector, who can step in on their own to document failures to meet decency standards. At the same time, you have the option to withhold part of your rent (the amount depends on how serious the problem is) and set that money aside in a separate account. You can also have the installations repaired at your own expense and deduct the cost from your rent, but it's better to do that after sending a formal notice first.

As a last resort, there's mediation with a mediator or legal action in civil court, where you can claim damages for the harm you've suffered. The key thing is to document every step and not let it drag on, especially if it's winter and you're freezing.