thanks a lot for all your opinions...after reading your views i managed to have a talk with the guy.
i just wanted to let you know how are the things now...
i got the promise in writing, in an e-mail, and the HR people are starting the procedures for my work permit.
if i don't get the work permit, there is still a back up option for me to get the job - as a trainee for a few months, until the work permit will be ready...

i don't have the contract yet, it is true...but after this, i can say i totally trust the guy, and i think Swiss people are trustful...and their word is believable (at least much more then my co-nationals trustfulness in job offers)

i will keep you posted