will it be possible to have a temporary working visa without a job offer? or, will it also be possible to have a job offer even without a job offer?
You can only get a temporary work visa without a job offer (open work permit) is if you are on some kind of exhange program, for example bunac or if you are the spouse of a temporary skilled worker or the spouse of a student. I do not see how you can have a job offer without a job offer?