Today, I am describing only a very small change, but nevertheless a very important one (for me). Generally, all important IT-related instructions and documents are created in english in the first place. Therefore, translations into other languages are not always ideal.
So I always recommend, no matter what you are looking at and learning, to do it in english.
This saves you afterwards a lot of time and effort to relearn, as you should generally set all your systems to english by default. Here are instructions on how to change the vSphere Web Client.

First, log in with your credentials.
At the top right of the bar you can see which user you are logged in with.
Click on the small arrow pointing downwards to access your personal settings.

In the 2nd tab, you have the option to specify the language.
Normally, the language depends on the browser settings, which are inherited to the vSphere Web Client.

The following screen shows how to overrule this setting.

Refresh the Browser pressing "F5" or using the "Refresh Button"