Belgian pension

Without really knowing the terms and conditions of your court ruling, it's difficult to provide any advice. Surely the best person to ask in this situation is your lawyer.

The basic arrangements for Belgian state pensions are done by mutuelles.
I don't know whether all mutuelles offer the same support but mine has a regular info session at the local branch office for people with queries about pensions. If such a service is offered by your mutuelle, that is the place to start as it will be free.