Is there a way to get stronger withouth lvling up? a friend of mine said that losing duels from stronger people makes me stronger but nothing happened at all, can someone answer please? :/

i think tactic wise.....you'll learn from your mistakes and probably will come up with some good combo and tactics

Like you won't learn anything from fighting low levels but if you fight people higher levels then you you can learn alot.

maybe thats what he meant

This^

You dont not get stronger from losing duels stats wise. you just play smarter assuming your paying attention.