She left me with a broken heart that still loves her, however it was my fault by cheating on her but asked her for forgivness and another chance many times, She refused left me and fond another guy and now they are engaged. Please show me a way to be with her again how to make her leave her fiance and marry me?
You don't get a second chance with many things in life. Especially when you screwed up the first time. Why would she want to give you a second chance? She is engaged now, dude! You can stay fixated on her forever, or you can move on, but you can never have her again.
There's no way to get her back. It's over. Better just accept it as soon as possible and realize it's not happening. You cannot live in a dream world anymore. The reality is she has moved on and in good time you will move on as well but you first need to accept the truth for what it is.
Sorry, there is no way this will happen. You put her in second place for a short while, and that's the best she'll ever feel. If she was "the one", why the hell did you risk it all by cheating? You gambled and lost big time. Just accept it and move on yourself. Learn by your mistake!!