Am I a jerk?

I play until the end - you're gonna have to mate me if you want the win.
I don't give moves back - you make a move, live with it.

Am I a jerk?

No, you aren't

Most of the time ('you're gonna have to mate me if you want the win.') you're just wasting your time. But you probably scored some draws instead of losses with that strategy. :-)

And you have to do it in the given time. Basically the rules of the game.

I mean if I manage my time better than my opponent, would should he get the win just because he's up material? :-)

@SilverBullet: exactly.

Playing until the end: In a Lichess tournament when time is a key, then you probably are.

Don't giving moves back: That's the rule. Nobody can claim the execution of an exception as it was a given or earned right.

So, yes and no.

I correct myself:

If you managed to get a time advantage as a clear sign of superiority, then winning on time can't be critisized, even when the other side is ahead on material.

So, it's a relative thing. But, anyways, everybody can tell sometimes playing 'till the end it's a jerk thing.

I think it's even less jerk-like to play on in a worse position in tournaments, when stronger players often seem more on edge. Ive beaten far more opponents above my rating in tournaments than from the lobby.

As for takebacks, I turn them off in rated games, so it's the same for me or my opponent. Opponent's mistakes and mouseslips and mine are equal that way.

I would conclude you're not a jerk, no.

You might be a jerk, and probably are on occasion, but not necessarily because of your preference or style of playing online chess, within the rules.