I would say use long time controls. 30 min, maybe some games where you can think for 1 or more days per move. Those games are excellent to try to find the best move for your strategy/plan.
Duration of a game to learn ?

Start with standard time controls ( 15m+10s ) and try to make sense of what's going on. It is also good to play correspondence games.

Well there's a question of speed vs quality (of learning) and what your ultimate goals are.
Blitz is great for new players to test their openings and experience many games.
Blitz is bad for players who play too much and simply keep making the same mistakes over and over. (Also bad if it's too fast and you end up making random moves or losing on time every game).
Long games are great for all players, learning good lessons slowly when the lessons are more likely to make it into long term memory.
Depending on your goals and patience, find the right balance for you.
Standard chess works well for inexperienced players. You might want to try out 30|0 and when you get the hang of it, you could try out 15|5 or even blitz games.
Hi,
I'm a beginner and I don't know which is the best duration of a game to learn correctly ?
Thank's