I am an IT professional who recently relocated to Berlin, Germany on Bluecard(Bluecard is still in the process though). If I switch jobs within 2 years of relocating for better financial and technical prospects, I understand I need to take approval from the Immigration authorities ([https://service.berlin.de/dienstleistung/326856/en/](https://service.berlin.de/dienstleistung/326856/en/)).
How difficult is this process, mainly is it just a notification to authorities or a kind of approval where they can reject it as well? If they do reject it and I have already joined the new company, then what?