Im a Preiest, and in act 2 i have no idea how to promote i have done the quest (undead in the sewers) and there are no diolog trees anywhere about it, some can help? i dont even know who to talk to

There are actually two quests pertaining the sewers. One is given to you by Sheriff Smith and to complete it, you have to kill enough undead in the sewers. The other quest, the promotional one, can be given to you either by Judge Welfhar or Cardinal Truncquillius, and to complete it, you have to find out who is responsible for the undead in the sewers.

Have you found Harph's diary in the sewers and have you discussed it with Tinthan?

I'm also a priest. Spoke to Truncquillius and gotten the promo quest. Have Harph in custody, got his diary, haven't tortured him yet, and haven't talked to Tinthan either. Checked with Sheriff and that quest (undead in city) is done. So I keep Harph in custody for now, until I get Tinthan's testimony? Then trial and burn Harph?

I've messed up with this Harph quest where I have Harph's diary and I talk to Tinthan without putting Harph in jail first. When I went to arrest Harph later, he summoned skeletons and I had to kill him which meant I couldn't get his confession under torture and burning.

I believe it doesn't matter if you kill him or burn him. Both ways will allow you to complete the promotional quest successfully. All you should need is Harph's diary and Tinthan's testimony. What happens next depends on when you get Tinthan's testimony. If you get it prior to your attempt to arrest Harph, he will attack you and you will have to kill him. If you get Tinthan's testimony after you arrest Harph, you will be able to burn him at the stake. But if I'm not mistaken, there is no need to torture Harph because there is nothing more he could tell you.

Welfhar does not give me the promotional quest in this game and Truncquillius is no where to be found in my game. Though i assume he is not there because i am at the last stage of the A2 main quest.
But if noone is there to give me the quest does that mean i am unable to get promoted?

To get promoted by Judge Welfhar to Inquisitorial Judge you need to finish a quest for him (concerning the undead walking the streets of the city at night) and correctly answer all his questions. To get this quest it seems to me that you have to get warrant for Cardinal Truncquillius first. As soon as you get the warrant from Welfhar, Truncquillius runs away to Glatzburg's Episcopate Dungeon (that will become accessible at that moment thanks to a new priest standing in front of the locked door there). I think that at that moment you should be able to ask Welfhar about the promotional quest. Of course, you have to be Inquisitorial Prosecutor to be able to aspire for the Judge position.