I chose Transmute Master but haven´t complete the quest. Can i chose an other one instead? I have completed the first step of the quest, the one i got to speak with some guy in netherstorm but i I´m not done with 4x Primal might.

have you tried going back to the guy that gave you the quest to talk to the x-mute master trainer?  if you cant get the other quests from him, the potions master trainer is at the cenarian refuge in zangarmarsh.  I'm not sure where the elixir master trainer is.  you will probably have to abandon the xmute quest.

elixir master is in shattrah the skettis guy or whatever if im not mistaken

Elixer master quest can be got for honor hold in hellfire