Considering an opportunity to move to Riyadh

1. How long does it take to get an official offer (letters, contracts, visas etc.) after a verbal offer?

Depends on how much "wasta" your employer has.  Could be 30 days, could be 6 months.  Closer to 30 days, though.

2. As i understand life in a compound (i am european) would be safer and more comfortable. And a price for 1 bedroom apartament would be around 65000-85000 per annum?

Depends on what you want out of your time in Riyadh.  Many Europeans find that renting an apartment is more interesting.  Depends on the benefits you get for housing from the employer.  They may provide housing, they may provide enough money for an apartment and furniture.  There are apt. buildings that are mainly foreigners if you are worried about living among the locals.

3. What details should i be provided by my employer, and what should i ask for?

Employer should provide: Return ticket each year, health coverage, bonus at the end of contract and perhaps housing and transportation (car or car and driver or car allowance).  That really depends on you.

Thank you very much for your answer! Will keep that in mind. What about the Banks in general, maybe you know about or heard of how do they treat their staff?
And about the worry of living with locals, i am ok with it, but i don't want to be inconvinient for anybody.

Somebody knows job hiring in riyadh for finance, human resource and quality control inspector?those who in need pls mail me thanks

Hi mshumanatomy, welcome to Expat.com!
You should post an ad in Riyad's Classifieds -> Jobs section.
Good luck
Arlette