Can I call the bank guarantee without going to court first?

In most cases, yes — that is the whole point of an autonomous bank guarantee. The bank's obligation to pay is independent of any court proceedings, and you can present your demand to the bank as soon as the trigger conditions in the guarantee document are met (typically arrears of a specified amount). However, check your guarantee document carefully: a minority of guarantees issued for residential leases contain a clause requiring a court order or a signed declaration of default before the bank will pay. If your guarantee has this requirement, you will need to obtain that document first.