Hello, LutzBruno, and welcome to the Simple English Wikipedia! I hope you will be happy helping here. You should begin by reading these pages: Wikipedia:Useful, Help:Contents, Wikipedia:Policies and guidelines, and how to write Simple English articles. If you want some ideas of which pages to work on, read Wikipedia:Requested articles or the list of wanted pages.
Even though it is a good idea to research an article (like looking at the discussion page) before making large changes, please be bold and try! Any changes you make that are not perfect can be fixed later. We are also working most on core articles and the most common topics until this Wikipedia grows.
If you want to ask a question or talk with other members, you can visit our version of the "village pump" at Wikipedia:Simple talk. Administrators on Wikipedia can also help you with more difficult problems. You can also ask me for help. The best way to do that is to leave a message on my talk page. You should always sign your messages on Talk pages by typing "~~~~" (four tildes) at the end of your words.
Good luck and happy editing!