New registration after total damage / vehicle class relevant?

If you have an economic total damage and want to get into the “genus” of the usage loss for the replacement period, then you have to let or do not care about a car of the same class. Background: Old VW Passat, replacement value 1600, residual value 300, economic total damage, but fully ready to drive, 10-12 working days replacement period, but for us ideal for “forest stories” because AHK and also not a pity when scraps come in. Grandma has a Twingo that you no longer need, I would like to let it on me. Or do you have to deregister its economic total damage? Are at least 12 days times factor X (vehicle class), does also a bit of something.