This is typical chicken-&-egg situation for many foreigners moving to Germany: landlords ask for a SCHUFA record for you to rent their flat, but you don't have one since you are not registered (Anmeldung) and can't open a bank account... because you don't have a place yet. If you are in this situation, you might want to go for a flat share (WG) and register there until you find your own place. You can also turn to services like Wunderflats, which lets you rent furnished flats without a SCHUFA record.