How can the two noble verses: ﴿Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills﴾ and ﴿But indeed, I am the All-Forgiving to whoever repents, believes, and does righteousness, and then is guided,﴾ be reconciled, and is there any contradiction between them?

There is no contradiction between the two verses. The first verse, "Indeed, he who associates others with Allah - then Allah has forbidden him Paradise, and his refuge is the Fire" (Qur'an 5:72), applies to one who dies upon shirk (definition) and does not repent. Whereas the second verse, "But indeed, I am the Forgiver of whoever repents, believes, and does righteousness, and then is rightly guided" (Qur'an 20:82), and the verse from Surah (definition) Az-Zumar, "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins'" (Qur'an 39:53), apply to those who repent.