Category B + trailer over 750 kg. Caravans, horse trailers, workshop trailers up to 3.5 t. All with just 5 mandatory drives and one practical test. You don't need any theory.
No. BE is a purely practical extension. Since you already hold Category B, theory is skipped entirely - you drive the 5 mandatory drives and go straight to the practical TÜV test drive.
With BE you can tow trailers over 750 kg, with the combination weighing up to 7 tonnes in total. That covers caravans, horse trailers, workshop and boat trailers. Above 7 t combined weight you need C1E.
If you're learning trailer driving completely from scratch: 2-3 practice lessons before the 5 mandatory drives. Anyone who's already moved a trailer before often gets through with the mandatory drives alone.