I have two SVG files. Both have layers that i wanted to keep. But when i import one document into the other i only have groups, but lose all layers. Is there a way to keep the layers or convert the groups to layers?

Currently, only sublayers are preserved when importing an SVG file (but need a trick using the XML Editor to restore them as normal sublayers) - see Bug #502075 in Inkscape: “Import Inkscape SVG loses layer and sub-layer information” for more details.

Guess i will stick with it. Maybe it's also possible to readd the group-information to the outmost layer.

Well, I typed a response to this yesterday, but it appears that something went wrong with the posting

....wait, did you edit your original message, or maybe have another topic related to this?
Oh ok, yes, a related topic