While we should forgive those who hurt us, that doesn't mean we must ignore the wrong they've done or the laws they've broken. What your business partner has done is serious and very wrong; in Old Testament times a thief, "if he is caught, must pay back double" (Exodus 22:7).
In other words, forgiving someone doesn't necessarily mean we approve of what they did or act as if it didn't happen. A person is still responsible for what he or she did, and they may still have to suffer the consequences. King David sinned when he committed adultery with Bathsheba, and eventually he confessed his sin and God forgave him (see Psalm 51). But he still had to pay the price for his sin; the son born of that illicit union died, and David's power was diminished.
I know this is a difficult question and, of course, I don't know all the facts. However, don't forget the Bible's warning: "A man reaps what he sows. The one who sows to please his sinful nature, from that nature will reap destruction" (Galatians 6:7-8).
Yes, forgive your business partner in your heart, just as God has forgiven you. But don't let him talk you into something that isn't right or wise. If he truly feels sorry for what he's done, and has repented of it and sought God's forgiveness, then he will want to do all he can to pay back what he has stolen.