Extension of schengen tourist visa

Ask the person you applied do, don't hold up much hope, it is outside the rules to get permissions to stay.

I did not do it miself but according to this web-site https://www.schengenvisainfo.com/how-to-extend-schengen-visa/ usually, your visa extension application can take a few days, up to a month to be processed by the relevant authorities.
BUT! Since Belgium is quite unpredictable country regarding admin processes you better ask the commune where you applied for it. or if you received any confirmation of reciept from the commune, it could be written there.
Just bear in mind that it is not the commune deciding on your visa extension but the Ministry of Interior, so you migh want to call there and ask. Good thing is that while you are in the process of wiating you are allowed staying here.