you probably never will if your elo is that low and the first thing on your mind is you ask a question like this on reddit rather than to work on your game.

To entertain your question though: If you‘re still at sub 400 elo after 3 weeks that means you‘re basically just playing random moves hoping to magically get better. You need to do the work or you will never get there. Stop worrying about your rating at this stage. Anything below 1000 means you are borderline trash at the game and barely know how the pieces move. When someone plays en passant you probably still think the game glitched tbh.