I'm a Flemish Belgian, but not living in Belgium for many years. So I would be of limited use.
BUT note that, as German is the 3rd official language in Belgium, practically all laws and regulations are also published in the German language. This could save you a lot of time.
If you need to set up a business, approach a good accounting office, rather than a lawyer: they know the rules, and can help you with your administration, registration, VAT-registration and your regular tax filings. You're going to need them anyway.
Good luck!