I think I have it configured your way now... English and Dutch.
As before, I use yellow color to indicate "preferred language" (default app language) setting, cyan to indicate region setting and red for errors. As you can see "This is your 365" is written out in English on the Home tab, but it's also written in Dutch as "Dit is jouw 365" on the Productivity tab. This perfectly normal, and it's not a problem of Windows but of the Microsoft store itself and Microsoft has unfinished work to do here.
Do you normally type in English or Dutch? Maybe both? If you get back to me I can try help you set that up so you don't have to give up for example Dutch keyboard layout for the benefit of US English display language. I will show you now how I have set this up.
The very first thing I did was to download "Nederlands (België)" language package, and I chose to set it as my default display language (affects classic Windows applications like Explorer, but not modern apps like the Store).
After installing it I had to sign out and then sign into Windows again to apply the changes.
België is my choice of country and Nederlands (België), i.e. nl-BE is my regional setting.
My Windows display language (Explorer, etc.) is Nederlands (België), my preferred language is Nederlands (België) and this is the most important part that affects the Store app.
The reason that English is displayed in Store and not Dutch, even though Nederlands (België) is higher up in the priority list is because it does not have all the language components like English (United States) has. So the Store falls back on whatever is next best thing available, which is why we have this priority list – the Store picks up these components in the priority they are listed here.
You can add language components by clicking on one of these items and then clicking Options (Opties).
The missing component must be Spraak (Språk in Swedish).
And now we have it...
So you should be able to turn the navigation menu and the like in the Store to Dutch. I have not tested this yet.