Yes, as explained when you first reported this problem, this is not a problem with Dorico, but rather with the MusicXML files exported from Sibelius. The MusicXML files you are exporting from Sibelius do not contain chord symbols, so Dorico cannot import them as chord symbols. Please try the Convert Legacy Chord Symbols plug-in, as recommended in that thread, and then re-export your MusicXML files from Sibelius, and import them into Dorico.
Please post an example of the problem that you’re having, Peter. I hope you will understand that writing “slurs!!!” as a description of a problem, it doesn’t give us a lot to go on in terms of making sure that we can assess and potentially address your problem in future. As it is, I think Dorico’s slurs are, in general, excellent.
It will take you two minutes in a text editor to whitelist these VST instruments. Stopping using Dorico for the want of adding three lines to a text file seems, if you will forgive me for saying so, like cutting your nose off to spite your face.
As for German documentation, I certainly agree that this is lacking at the moment, not only in German but in all languages. But we are making good progress on fleshing out the documentation, and I expect that we will have complete documentation for Dorico in all languages early next year.