JavaScript coder needed

I have a 9mb obfuscated encrypted JavaScript file. I either need it to be fully decrypted and returned to its original state as there is things i need to change in the code and there is a backdoor I do not want. Either that or decrypt it as much as you can and then make something similar which is readable to me and editable with the same functionality. I will only pay once I see everything has been done and completed, scammers stay away!