What game length do you think is best for beginners?

I have tried mostly 10min because It looked standard but maybe I am mistaken.

I think 10 to 15 min is a good time to play chess for beginners

Well, 15|10 is best I think.

Enough time to actually think about your next move properly.

Without any increment at all you cant really play a good endgame.

Also its not excessively long yet either.

15|10 or 30|30

IM John Bartholomew recommends at least 15|10 minute games for chess skill improvement. The man knows what he is talking about.

I cant pick 30|30 from my list of choices. Is that a diamond thing ?

Thank you for those answers.

15|10 is best.
It is the official rapid time control like for the Rapid World Championship.
Thanks to the increment you always have 10 seconds / move to win a winning position or draw a drawing position.

25'+10"

10 min, cuz' this will also help them to experience chess with different opponents and also teach them to think and act quickly

It`s a custom time control. But 15|10 or 10min are some of the best choices

I like to play 15 | 10, or 10 | 0 if I don't have too much time. Anything lower than that and I notice a huge decrease in my performance.

30|0 offers a good balance.

10|0 and 1 and 3 day chess is pretty good actually I often find that with long time control like 15|10 or 30|0 it is just to boring for me personally. I often say that begginers should never even go close to 1|0 or 2|1 or 3|0 or 3|5 it just isn't good for begginers!

on my first time, i reached pretty high when i played 30|0, then moved to 15|10, then 10|0. u can try that. 1 month of 30|0, 1 month of 15|10, and 1 month of 10|0.