HU/AU date is in the deregistered period

I didn’t know where it fit best! I’ll register my BMW next week and I have to register it again when I say it’s ready and fit from me. So it might be June or something. In between, my HU/AU appointment is in March. I have to go there, or how does it happen if I want to register my car 3 months later, after HU/AU has expired again… And how do I get my car to the TÜV? I hope you can keep going. Eleven!