-Is there a quest to the guarderd compound in temple district, or should I just enter and slayer everbody?
-same for this big building in bridge district......

-In the sun temple (?) at the temple ruins area(umar hills quest)I found a piece of some diary, with some notes about a treasure in one of these rock columns. But I could not find anything.

-How do you completely kill an Ilfrit? They turn into smoke, which I can not seem to do any harm.

Thanks st.Schnupps

Nothing to be said about the guarded compound. Just kill everyone. I don't know which big building in the Bridge district you're talking about, though. If it's Saerk's home, no, you don't.
Don't know about the treasure at the temple of Amaunator. I've seen this question a few times, though, and from what I've heard it might have some connection to one of the ranger quests or somesuch.
Efreeti will turn themselves into mist to recuperate if at any time their health goes below three, but above zero. In other words, if they're on 23 health and you hit them for 20 damage, they will turn into mist. If you hit them for 24, though, they will die.

Is the tresure in he umar hills Anything to do with Mithril? If it is then you cant complete this quest unless your a ranger and you have the ranger cabin as stronghold

The house in the bridge disrtict i *think* you're reffering to is linked to Amoen....if you have him in you're party of course

The House in Bridge District is called "Home of Saerk Farrahd". But don´t worry about it I went through there and there´s nothing worthy in it...
Thanks anyway st.Schnupps