@aemylt as a French person who grew up near the Belgian border (in Lille), I prefer to speak English when I go to the flemish part. They generally speak very good English, and often good French too, but not always, so you should not assume that they do. There's also an anti-Walloon and anti-French mentality there sometimes. I don't think many Flemish actually speak German, although they might grasp some of it due to linguistic proximity.