As a physician practicing radiology and ultrasound, am I permitted to teach a gynecologist how to use an ultrasound machine, knowing that she will use it in her clinic and charge patients fees, despite the fact that I am not a specialist and consider myself in need of learning?

It is permissible to teach your friend the profession if you predominantly believe that she will not undertake any action until she has verified its correctness, while clarifying the danger of medical error and that "whoever practices medicine without having been known to practice it before is liable," and emphasizing to her the necessity of referring to specialized doctors and consulting them to avoid harming people, based on the hadith "There should be no harm nor reciprocating harm."