My bollard features 3p-Technology and is constantly being knocked over. Is there a way of firmly mounting it in?

Yes, there is. You can convert the existing bollard (featuring 3p-Technology) to a junction piece without pre-determined breaking point. This type of mounting provides the usual resistance of conventional, fixed installation, but (due to the system) can still be removed.
Alternatively to the 3p mounting, ABES also offers every bollard model with a base anchor which can be cemented in.