I have DNA matches from Ancestry, FTDNA, GEDMatch, and My Heritage. My half-sister also tested with Ancestry. It confirms we are half siblings and share the same mother. I do not know who my father was, so in my search, I realized that ALL of my DNA matches are shared with my half sister. I was trying to isolate those matches we don't share, in hopes that I could find my father and/or relatives. I am new to genealogy, so I don't know if I am way off in this understanding.
How can this be that all of our matches are connected in some way?
How can I find my father in this case?
There are so many features of GEDMatch that are too complicated and advanced for me.