Our sins are forgiven
Let me encourage you to read Isaiah 53 the entire chapter, and then OMYA you will see that the LORD of Isaiah 43:11 and 45:22 is the same person who is here described as the Suffering Saviour. Read the OT law and read of the atonement that was required as part of the sacrificial system to atone for the sins of man, and you will see that the lamb of the sacrifice is
"led like a lamb to the slaughter" (vs 7) and "my righteous servant will justify many and he will bear their iniquities".
Why do we keep sinning after we become Christians and know our sins to be forgiven.. well look at the words of Paul in Romans 7. As a Christian, and a Jew, he was under no delusion that he wouldn't keep on sinning.. and why? (romans 7:7ff) "for what I want to do, I do not do and what I do not want to do I do". At it is, it is not longer I myself who do it, but it is sin living in me. (vs 16-17).
See Paul knew what every human being ever born knows.. no matter how hard you try.. you cannot stop sinning. We are born with a sin nature and we would die with a sin nature. Only one thing can stop it .... "What a wretched man I am! Who will rescue me from this body of death? Thanks be to God- through Jesus Christ our Lord! (Vs 7:19 -20)
Yes.. God is our saviour... through Jesus Christ our Lord