Actual gross weight of the trailer
Field F.2 of registration certificate part I
For the licence, the permissible mass counts, not the actual weight.
Reserve
300kg
300Your trailer at 1,200 kg is below the limit of 1,500 kg (braked).
Permitted
The braked towing load applies: 1,500 kg.
What you can do
Class B is enough (combination 3,300 kg)
Under § 6 FeV: class B up to a 3,500 kg towing vehicle with a trailer up to 750 kg or a combination up to 3,500 kg; B96 (§ 6a FeV, driver training) up to a 4,250 kg combination; BE up to a 3,500 kg trailer. The permissible total masses from the vehicle documents apply.
Trailer Load Calculator by Rechnerzentrale(opens in a new tab)