There are people who are still confused about the meaning of God Almighty sending a new messenger.
I have explained more than once that the Mahdi will not come with a new Qur’an or a new Sharia, but rather he will rule according to Islamic Sharia, and God Almighty will send him with missions other than what you understand, including making Islam prevail over all religions, and preparing and giving good tidings to the people for the descent of our Master Jesus, peace be upon him, just as our Master John, peace be upon him, prepared the way for our Master Jesus, peace be upon him. These are the two main missions of the Mahdi’s message, in addition to his warning the people of the torment of the smoke, as I explained in my book.

This is part of my book.

The similarity of Mahdi's life to some of the prophets:

The Prophet (peace and blessings be upon him) said: “You will follow the ways of those before you, inch by inch, cubit by cubit, to the point that if they entered a lizard’s hole, you would enter it too.” They said: “Who are they, O Messenger of Allah? The Jews and the Christians?” He (peace and blessings be upon him) said: “Then who are the people?” (Agreed upon). As we mentioned previously, there is a great similarity between the state of the Islamic Ummah and the state of previous nations, and there will be another similarity between the lives of the prophets of previous nations and the life of the Mahdi. By following the life of the Mahdi through the hadiths, verses of the Qur’an and the traces, we find that the life of the Mahdi is similar to the life of our master Moses in some of the miracles with which Allah Almighty supported him, such as the swallowing up of the army that wanted to kill or capture him. Also, both of them were loyal to a weak nation, so they rose up with them, and their call was similar before tyrannical rulers without fear of their punishment.
There is another similarity between the biography of the Mahdi, our master Solomon, peace be upon him, and Dhul-Qarnayn. Al-Suyuti said in (Al-Aref Al-Wardi fi Akhbar Al-Mahdi): Ibn Al-Jawzi narrated in his “History” on the authority of Ibn Abbas, may God be pleased with him, who said: The Prophet, may God bless him and grant him peace, said: “The earth was ruled by four: two believers and two disbelievers. The two believers are Dhul-Qarnayn and Solomon, and the two disbelievers are Nimrod and Nebuchadnezzar, and a fifth from my family will rule it.” This is what will happen with the Mahdi after his victory in the great battle.
There is another similarity between the Mahdi’s ordeal and the ordeal of the rest of the prophets and messengers, and that is in his severe ordeal at the beginning of his call when he calls people to Islam and they accuse him of being a magician or a madman or that someone taught him what he says. He will also be denied when he tells them that he is the Messenger of God because the majority of Muslims have believed for centuries that the message has been cut off. Therefore, I believe that the Mahdi will be severely denied at the beginning of his call, just like the rest of the messengers before him.
The Mahdi will also suffer another calamity by losing his great conquests after the appearance of the Antichrist. He will only be the ruler of Mecca, Medina, and Jerusalem. In addition, a large number of people will be tempted by the Antichrist after all that he has achieved in returning people to the obedience of God Almighty, just as happened with our master Moses, peace be upon him, when his people went astray and followed the Samaritan. The same events will be repeated with the Mahdi in the future as well.
There is another similarity between the Mahdi’s preparation for the call of our Master Jesus, peace be upon him, and the preparation of our Master John, peace be upon him, for the call of our Master Jesus, peace be upon him. The Mahdi will be a messenger before the descent of our Master Jesus, peace be upon him, and he will prepare the call for him and prepare the people to receive him. This is what our Master John, peace be upon him, also did with our Master Jesus, peace be upon him. It is also possible to add the similarity in the killing of our Master John, peace be upon him, by King Herod, one of the kings of that time, with the killing of the Mahdi by the Antichrist, as we assumed the possibility of that before - and God knows best.

This is part of the chapter on the Messenger Mahdi from the book The Awaited Messages, written by Tamer Badr.

Please do not rush to judge the book before reading it.
I have published my book, The Waiting Letters, as a charity for the reconstruction of mosques.