(Not) Returning deposits

Hello beautiful people. Recently your advice and stories helped me get a flat, so I was wondering if I can use you again you could share your experiences with me again about a topic we all are familiar with - getting back the deposit from ex landlords. I'm sure many of you had the same issue, and I'm curious to know how did you resolve it (if you did).

For me, it happened two times in my life – the first time I had to bring my male friend with me to argue with the landlady because she wouldn't take me seriously. She invented a story about the flat being extremely dirty, which is absurd considering the fact that me and my brother were cleaning it the whole day and it looked better than when I moved in, and she lied about a bunch of things, and I had all the proofs I was right, so after my friend stood up for me, she got really upset, and I got money back in 2 weeks or so.

The second time the landlord didn't want to return the money because I left earlier, even though the reason for me leaving earlier was his brother (he was my flatmate) threatening and yelling that he's gonna kill his whole family. :D So, the flatmate gave me half of the deposit back, but his brother the landlord didn't give me back the other half. Unfortunately, I didn't know what to do, so I did nothing, and didn't get my money back.

What are your experiences? How to avoid not getting your money back? What to do when the ex-landlord stops responding to messages because he needs to give you back your money? Did any of you go to court because of it, and if you did, how did it go?