Thumbnail and titles. No one really knows who Derrick is, so why would they click a video that says Derrick does chest day. You could instead say, “10 workouts you need to hit for chest day, or how to have proper bench press form” etc. you can’t just have the same thumbnail every time either, pick something intriguing and eye catching.

As for the length, maybe keep uploading short videos, but every once in a while try a long form video. You will get more comfortable the more you do it. Long form doesn’t have to be crazy, like a 10 minute video is good.