Relocating as a remote contractor

Hi, so there is a bit of a backstory to this question but I won't bore you with it! The jist is: 1. I want to move to Switzerland. I work for a German company, and currently live in Germany, but they would be willing to let me base as a contractor/B2B in Switzerland while still working for them. Is it feasible? Are there any legal hurdles to look out for? 2. If I move to Switzerland, I need to continue treatment for a knee injury complication. Considering it's a pre-existing condition, would it be cover by an insurance policy or would I potentially face out of pocket costs if it comes e.g. To another surgery?