Hazrat Mahdi (as) will not know Arabic

As a matter of fact Tirmidhi said the following about Hazrat Mahdi (as) in his book called Khatm al-Awliya (Seal of Saints):

“Just as the last of the Prophets, Muhammad (saas) was given the "seal of prophecy" (Khatam an-Nubuwwa) and he is a deed of Almighty Allah over all Prophets, this guardian [Hazrat Mahdi (as)] who is the last of the guardians will be so in the End Times.”

Muhyiddin ibn Arabi his book called al-Jawab al-Mustaqim (The Straightforward Answer) written to answer the questions asked by Tirmidhi in his book of Khatm al-Awliya:

“He [Hazrat Mahdi (as)] is someone who acquires the truth and closely resembles his forefather [Muhammad (saas)]. HE DOES NOT SPEAK ARABIC VERY WELL, but he is no different to him in moral terms. HE WILL BE OF MEDIUM HEIGHT. THE AGE OF PROPERTY WILL COME TO AN END WITH HIM, AND SOVEREIGNTY WILL END WITH HIM. He [Hazrat Mahdi (as)]will have a helper called “Alive”. His essence is spiritual, his appearance is humane. (al-Jawab al-Mustaqim amma Seele anhu at-Tirmidhi al-Haqim, Bayazid, no: 3750, leaf 242b)