Decoding a MD5 hash based on a given formula

I have a task with MD5 hash. I made an API call to the server and was able to get hash. Right now, I have to solve the hash and send my solution to its address.But I have never seen a problem or a coding task like this. Can anyone give me a help with this ?

import fetch from "node-fetch";
const crypto = require('crypto');

const GUID = '6a21be94-c29f-41e1-aa59-0a1029644872'
const SLUG = 'baris-savas-91533'
const baseApi = `http://career.dijitalgaraj.com/hash/${SLUG}`

const apiRequest = async () => {
    const response = await fetch(baseApi, {
        method: 'PUT',
        headers: {
            'Content-Type': 'application/json',
            'X-GUID': GUID
        },
        body: JSON.stringify({
            GUID: GUID
        })
    })
    const data = await response.json()
    return data.hash
}

const HASH = await apiRequest()
console.log(HASH)

//We have splitted the hidden email address into multiple substrings, starting with first two letters and increasing by two letters in each iteration. For example:
// hello@dijitalgaraj.com => he hell hello@ hello@di hello@diji ... hello@dijitalgaraj.com
// We'll refer this substrings as "x" in the following clause.
// Each substring is hashed with the formula: md5(md5(your_email_address) + x + md5(x)) and then added all together as the hash.

// Using the information above, solve the hash, find the hidden email address and send your project to that address. The address is created uniquely for you.

This is the step that I can't proceed.And also it says in notification ==>

1-The mail address can contain numbers, all english letters and special characters: + - . _ @ (understood clearly )

2-Don't try to decode or reverse-engineer md5 hash to solve the problem. ( And here I don't know what to do )

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