Has somebody a Familysearch powerpoint presentation for beginners?

Johan - Here is a good starting point where you are likely to find what you're looking for: https://www.familysearch.org/en/help/helpcenter/landing

Is this just for your own learning or for teaching others?

I don't have any suggestions for Dutch, but here are a couple of options I can think of:

A. FamilySearch has collected Help Center articles about the basics of FamilySearch onto a single page here: https://www.familysearch.org/en/fieldops/quick-start-learning-lessons-table-of-contents Many of these have videos with them.

B. The BYU Library Family History Center has dozens of high quality presentations about FamilySearch that you can access on their website or in YouTube such as this one: https://www.youtube.com/watch?v=oNYa_u3v_c8

You can check through them on their channel: https://www.youtube.com/@BYULibraryFamilyHistory or on their website: https://familyhistory.lib.byu.edu/learning Here is one of their virtual classes that is about beginning on FamilySearch: https://familyhistory.lib.byu.edu/virtual-classes/lighting-a-fire-class-2-introduction-to-familysearch

If this is to develop your own teaching presentations, when you find a presentation that fits what you are trying to do, you could try contacting the library or the presenter directly and ask if you could obtain the slide deck and permission to translate it and use it.