I can say basic things in it now, but not exactly fluent yet. I tend to study 15-20 min every day with this app. It does a mix of vocabulary building, grammar, and pronunciation exercises. I want to get to the point where I have a bit of a base to start from, and then once I'm using it on day to day basis it should go smoothly from there.

And it's my fourth language, I'm fluent in Russian and English, and I used to be fluent in Czech, but haven't used it in decades so forget most of it now. Mandarin is a very different experience though. In some ways it's easier because you don't have to deal with stuff like conjugation, and grammar is pretty straight forward. On the other hand, reading and writing takes a lot more work, and a lot of words sound similar or even the same while having completely different meanings. So, context becomes really important.