It is easier than you think. Justs navigate to Stores > All Stores and you'll see the Create Website Create Store and Create Store View buttons. (here is a picture:https://prnt.sc/t5k9hn)
Start with the creating Belgium website. Then create a Belgium store and assign it to the Belgium website and after that create different stores assigned to the Belgium store.
It is all done gradually and there is nothing hard about it creating them. You set all of the necessary information while creating a website, store and store view.
It becomes a little tricky when you start to configure the language and currencies for them.
Here is the guide on how to go through all of the processes of creating a multi-language website:
https://magefan.com/blog/how-to-create-multi-language-store-in-magento-2
And here are some extension you might find useful in this process:
https://magefan.com/blog-/magento-2-must-have-extensions-for-multi-language-store
