Are you just passively watching right now, or are you trying to write things down and repeat them? The thing is, just listening in the background is pretty much useless - you need to actively engage with the material.
Try channels like English Addict with Mr. Duncan or Learn English with EnglishClass101, where the teachers specifically break down phrases and repeat them several times - that sticks in your head better.
The key is to watch with subtitles, pause, and repeat out loud after the speaker, even if it feels weird. I used to think it was enough to just watch TV series too, but when I started repeating and writing down useful expressions - that's when it actually started working.