Language Translation Pack don't translate Theme and oc admin

I have a problem to change everything in mine Language(Dutch)
I downloaded the Language Translation Pack Dutch.
In International -> Languages the front and back office are Enabled.

In International -> Translations -> I Create or update translations -> Dutch, Core, Core & Backoffice. The last where my selections and everything is in perfect Dutch.

But If i want to add it to; Theme, Stater Osclass Theme, I have no Translation.

So I didn't translated everything. Like the admin and parts of the website. I have the feeling I missing something which I can fix within 1 minute. Problem is, I checking already 2 days.


Extra information:
I used OsclassPoint API Key
oc-admin is't translated, but sometimes it does for a moment...
In theme setting -> Category icons settings, the first 58 field are translated. The rest not.
I use Starter Oclass Free Theme, but I also still have Sigma Osclass Theme not deleted.

Translation consists of core (you downloaded), theme and plugins translations.

Yes they all there in the download.

But If I want to add it to Theme, it doesn't translate. See picture in attachment.

Its not translated, use deepl plugin

Thnak you! For me it was unlogic the last few didn't translated yet.

Make sure php max input vars is high enough if only part of translations is processed.

Thanks yes I saw it in the manual.