Also, I’m German, I do change the display language for my user to English. Most articles refer to the English version of the Lightning UI. The English language setting makes following tutorials easier for me.

Changing the language is done quickly, so you can try out which language settings fits your needs best.

List of supported languages

Currently you can select the following languages to change language setting in Salesforce.

Danish
Dutch
English
Finnish
French
German
Italian
Japanese
Korean
Norwegian (Bokmål)
Portuguese (Brazil)
Russian
Simplified Chinese
Spanish
Spanish (Mexico)
Swedish
Thai
Traditional Chinese

How To Change The User Language In Salesforce

Navigate to "Settings"

Click on your user icon
Click on the "Settings" link in the popup

Click on "Language & Time Zone"

The "Language & Time Zone" link can be found in the sidebar on the left.

Select the new language

Select the desired language under "Language"
Click on the "Save" button