How can I convert the laptop to German?

Internet is all in German, but if I start, for example, sytemsterung or so wants then see all of the English there, how can I implement all in German?

Is usually German.

You have a cracked Ultimate version. That is partly English, even after you have changed the language to German.

Win10? - Then try the following:
Go to Settings> Time and Language> Region and Language.
Select "Germany" as country and region
And with languages "German" off. - If this is not offered, go to "Add language" and search Germany (Germany)> Next.

This is not explained here in English, but with some English basic knowledge you will get ahead.