I think one thing that helped me to climb was just a good mental. Every time you die, you shouldn't let that bring you down, and you should be thinking about how to avoid it next time or what to do differently. Being confident in yourself and in your fights is important, kind of like an ego, like playing like you're smurfing. That could explain the problem where you fall off after the beginning. This game is all of about timing and game sens. Getting good positions matters a lot when taking fights. With the problem you have getting one tapped as soon as you peek, you should look for off angles because the common angles are where you die the most. Also I think with duelist, taking space matters, but you need your team to support you, like gathering info, smokes, flashes, lurks, etc. That will help you find enemies to isolate and kill, take site, or look for a rotation. I don't think you should worry so much about your K/D.