Reverse Engineering an encrypted app API

I need you to reverse engineer an APK (I will provide all the relevant decompiled files with .java code) in order to find how the requests transiting through the app and the API are encrypted, and I need a function in C# (native) AND in PHP (native) that will allow to crypt and decrypt a payload in order to communicate with the API. The request AND the response from the server is encrypted, and the two used algorithm might be very different.
The cryptographic algorithm used a very complicated. Please check the fill attached BEFORE bidding, it is a very complex job. The attached files are SAMPLE of the encryption used. You will also see a screenshot of the request, and the response, all encrypted of course.

The point of this job is to make a function so I can decrypt the response and get it in clear text, also a function to decrypt the payload so I can see what I sent over the network, AND an also a function for me to encrypt my clear text payload so it is accepted by the server.