2oGC3frj WTF Cryptography puzzle :D

This is my very first puzzle on the forums, really wanted to do this from some time ago.

Its a Cryptography puzzle, yea if you don't know what that is then ITS TOO HARD for you.

Rules:

You can comment your ideas and strategies, but no actual answers, ciphers, or code. If you solved it please do NOT post spoilers!

EDIT: do not share game nor links either.

EDIT2: The giveaway will end on Tuesday 6:00pm (GMT -5)

Hints:

• Don't bother with internet, books or anything, you wont find this form of coding.

• I didn't forgot anything at all.

Real Hint 1: The first line is the "Key"

Hint 2: The key is an encoded representation of the alphabet

Important Hint 3: the key is also "part" of the entire message. once you come to the end of the key, keep going into the message.

with this i mean that you should assume that the message needs to be decrypted in order, one character at a time. Basically, the first character in the message starts you off (the A in this case). the next character requires information from the first character to be decrypted, and so on.

Important for solvers: I realized a mistake, when you solve it the second letter should be ¨capital¨ , my bad.

I will place hints as I see fit.