question about the time gestion

Hi,

I've problems with games where time is about 15 minutes or less.

Several times I lose for time although I had a better position and advantage with material.

Is that playing defense is the best strategy ?
Playing faster to the detriment of the will to win the party ?
It's a little strange for me.

The reason is because you haven't familiariesed yourself enough with the positions, and 15 minutes isn't enough to calculate and learn the positions, once you've played enough slow games and learned the positions and patterns you will better understand new positions quicker, which is what rapid and blitz players do, but since you don't have enough understanding of positions and patterns, play with more time.

As @Magnus128 said, playing with much time really is not something you should be afraid of, it actually helps way more than bullet, blitz and rapid. There is something called the 45+45 league on lichess, this might be interesting for you: lichess.org/team/lichess4545-league

Thanks for your answers. It's more clear.
What is lichess4545-league ?