dude123 said:

is it possible to skip a quest? For example i have the quest where i should discover the dragonlady, but i would prefer to discover something else. But then i dont get a quest reward for that other thing.

Sadly, no. If you want these rewards, you have to do the upgrades in the order in which the game gives them to you.

On the bright side, Chinese units' upgrades are fairly quick and they're capped at level 20.