ok, thanks. I found this page already. But perhaps I need to go one step back.
So items are still there in openhab3. But I can’t fill them directly by http-binding?
Where Do I have to define the url.baseURL-object? Is it a thing now?
You now need to use the concept of Things with their Channels, and link those to your Items. Easiest thing to do is use the UI to create all this, but you can do it through configuration files. There are a number of examples already in the forum.