Revert a c# algorithm

Hi, I have an algorithm used for decryption. I need someone to revert it in order to encrypt stuff back. It should be really easy for someone with appropriate knowledge to do so. The decryption code is 100% working, you have all the tables and everything you need. All you need is to invert the logic. I attached an example of the algorithm (its missing the tables and maby 1 variable or 2). If you can do that please estimate a price and if you can do this withing 24hours (shouldnt take much time to do).