I have a Niederlassungserlaubnis. I am planning to move to my home country for self employment and pursue an external part-time PhD from a German university (will visit Germany once a year for progress review and discussion). In case my self employment attempt fails, I would like to come back to Germany to finish my PhD as a full-time researcher at the university and then find a job.
Do you think the Ausländerbehörde will agree to keep my Niederlassungserlaubnis valid in my case? Will it help my case if I have a Dauraufenthalt EU since it allows 24 months of absence for prior Blue card holders?