How to improve my time management and elo?

And can anyone suggest a good opening?

Your elo improving is a byproduct of better time management and decision making, in terms of getting better at time management I would recommend doing puzzle rushes, and playing a lot of bullet, at least that's what worked for me.

yeah when you played me you just spent way too much time. also, when you are recapturing a piece, premove.

I tried Blitz but that made my classical rating go down

Use the English opening it’s what grandmasters use

queens gambit is a good aressive line

Sicilian is too much theory, I honestly never recommend it because you always end up in a weird line were everything is too sharp.

Your elo won't improve in the long run until you get better at chess. That means making better moves, and time management plays a part of it. Now, to improve at it you have to first identify whether you're taking too much time or too little. If you're taking too much time, you may need to practice shorter time controls and quick thinking, or practice longer calculation so you don't have to double-check your lines as often. If you're taking too little time, you might have to learn more ideas and consider more candidate moves based on those ideas, or change your thought process so you always consider more than the first thought going into your head.

Good opening for which side? What situation? What style of play? How much time do you have to study? Should you even be studying openings? There are (generally) right and wrong answers to this question, but as I explain in my PSA for Beginners, often a player who is asking about openings is, to a great extent, asking the wrong question. In fact, asking about elo in general isn't exactly correct. Please give that a read. It could be helpful for you.

play anything that you feel comfortable and can blitz out a lot of moves in

If you need better time management, blitz could help… that and timed puzzle rush.

Don’t play too quickly, but remember how much time you have.

Maybe e4 or d4 with White

And with Black either e5 or c6 (against e4), and d5 (against d4)

As Sicilian was mentioned somewhere: it’s a good opening that can be played, but with your current rating it would not be a good idea (as the positions get complicated)

English opening

Sicilian Dragon on top 👍

I think that the London system is good for u

real

I can see you're 200, no need to learn any openings at that stage, just try to move your pieces from their starting squares towards the centre. Also, focus on making less one-move mistakes. Like attacking an undefended bishop with your undefended bishop, not knowing that your opponent's bishop can take it. Anyways, if you're hell-bent on learning openings, try the London

recommending bullet at this level is diabolical, only going to create bad habits.
I would start by only playing Rapid at this level so stupid one move mistakes can be more thoroughly punished and exploited. Increment (15+10 or 10+5) is preferable.