I had never done BJJ but I rolled with my buddy who trained and won a few wrestling and BJJ tournaments. I was able to defend all his submissions but when it came down to reversing him it was really difficult because of how heavy he was. When I tried reversing him he would turn the corner and put his weight on me. He's about 50 pounds heavier then me. If I train more in BJJ with black belts can I get enough technique to overcome a weight disadvantage?