Is it possible to make change on half match? ...One team member leave and another join ? or thats is norman and this is stupid question? :D hehe

you mean like at the end of a half? Yes aslong as the team memebers are green ticked and on your roster, ofc you can :)

Yes :D coz maybe one player is too bad and i need to change him :D

You are given 10 minutes of pause time to sort out connection issues or leaving members.

So aslong as you replace within the 10minutes you should be fine. Any longer the other team have the right to unpause and let the game continue.