Hi Markus Berchtold,
Please, find my answers to your questions bellow:
1) how to move pages in hiarchy. Drag and drop from the old 3.7
This is not yet available in Sitefnity 4.0 CTP. We are surely going to have this though.
2) how to link to external page
Unfortunately this is not available yet too, that is if you are talking about creating pages of type external in the site map.
3) how to link to internal page (not section)
Could you clarify on what you are trying to do, I am not sure I understand your question?
4) how to add pages in different languages
Localization (creating pages and content items in different languages) is not available in the CTP.
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