Do the Prophet Muhammad's visions of Allah in Surahs "An-Najm" and "At-Takwir" contradict the verses in Surahs "Al-An'am" and "Ash-Shura" which deny direct vision and direct speech, thus suggesting a contradiction in the Qur'an?

The Quranic verses (Indeed, he saw among the greatest signs of his Lord) and (And he certainly saw him in the clear horizon) do not indicate that the Prophet, peace and blessings be upon him, saw his Lord during the Mi'raj (Ascension). Rather, they refer to his seeing Gabriel, peace be upon him, in his true form, or to seeing the great signs of Allah.

As for Allah's saying (No vision can grasp Him), it does not contradict the possibility of seeing Allah, because "grasping" (idrak) means comprehension or encompassing, which is negated for Allah, while "seeing" (ru'yah) is possible. The Prophet, peace and blessings be upon him, denied seeing his Lord in this worldly life.