Hello everybody. I had some websites for a hobby but thats a couple off years ago. So i need te be updated with magenta, haven't worked with it before.
Hi @rens_jansen,
Welcome to the community forums.
The best way to start is to ask and try to help into the forums.
Since you have some experience with Magento you know you'll find information on StackExchange too, and (of course) you can start diving into the http://devdocs.magento.com/ (not only for learning but to correct and improve the docs) and the User Guide: http://docs.magento.com/m2/ce/user_guide/magento/magento-community-edition-2.1-user-guide.html
Another recomendation could be to be aware of Magento issues on Github: https://github.com/magento/magento2/issues.
Also, you must read this post: https://community.magento.com/t5/Welcome-to-the-Magento-Community/Start-here-and-hello-from-me/m-p/5... (in particular the guidelines)
Cheers!