I have lived in Belgium for more than 4 years. In general, you can find a big diversity of Belgian people. As I realized, Flemish and Walonians have big differences. Flemish people are more German-oriented, while Walonians are more French-oriented. I noticed that the former ones like organizing everything in their life and it is very difficult to get into their comfort zone, since they try to keep it as more stable as they can. Besides that, they are open only to persons that they know. So, spontaneous behaviours from Flemish people are almost non-existing, while Walonians are warmer people and they will talk or greed you even though you are stranger for them. Personally, it was very difficult for me to make Flemish friends and the only one Flemish person that can be considered a good friend has been living in Greece for 25 years so he has adopted the Greek mentality. I have also concluded that there are two types of Belgians: (a) those that like hanging out with international people and they do not like the conservative Belgian mentality, and (b) those that like hanging out exclusively with Belgians. Even in the second case, Flemish people would mostly choose Flemish people, keeping aside a Walonian person. These stereotypes have given me really bad impression about the formation of that society.
I have also noticed in Belgium that you should always organize in advance (1-3 weeks) your meetings even for a drink, otherwise you might stay alone. It was also very common to see single people in the bars and clubs. This has given me clear conclusions for the local society. Indeed, Belgians can be so introvert that they will choose to be lonely. While Mediterraneans invest on their social network and they try to meet new people without fear, Belgians do not trust easily and they will not let you enter their comfort zone so easily. Besides that, I have concluded that there is lack of national consciousness in Belgium so a Belgian person will rarely try to help a fellow citizen. I have experienced many times such behaviors and the usual answer was "It's not my responsibility". Even when I was meeting Belgians in other countries and I was chatting with them, they were trying to avoid me. I have also discussed with Belgians about the typical greetings that are rare in Flanders. Many of them told me that it's usual not to know your neighbors and not to regard them. Indeed, I have made a lot of efforts to organize a good social network including Belgians as well, but after some point I got tired and was hanging out with international and Greek friends.