I started learning Polish on YT as well.
I also want to learn Mandarin.
I watch Polish TV. I used to watch some of their serials, like “Klan” and “M Jak Miłość”.
I followed a fantastic Polish series called “Stulecie Winnych” which traced a Polish family from 1914 to 1989. I am now rewatching it with the Polish subtitles, and I find I understand a lot of it now.