“If we do not forgive/loose the sins committed by a brother on earth when they ask, that sin is bound on earth as well as in heaven and God cannot forgive/loose our sins against Him.”You are correct that I can forgive sins committed against me. Peter, however, can forgive sins committed against other people.
If Christ gave Peter the authority to forgive sins committed against other people as you state, it wasn't in the verses I supplied.
I would be extremely grateful if you would show verses where He did. Especially ones where Jesus gave Peter the ability to forgive another man's sin against God for God. Thanks BVB