What should one do who accidentally took money from his friend's Visa card and is now unable to return it, and will his repentance be accepted without returning the money?

Taking money from someone who has entrusted you with it, without their permission, is not permissible. It is a betrayal of trust and a major sin. You must repent to Allah and return the money to its owner. The fact that you do not possess money does not waive this right from you; rather, it remains a debt upon you until you repay it.