Will Allah forgive the sins of one who repents with sincere repentance, but still commits some sins and does not pray regularly, and believes that Allah will not forgive him because of his past actions?

Beware of ill-conjecture about Allah and despair of His mercy, for Allah is Forgiving and Merciful; He wipes away sins, no matter how great they are, with sincere repentance, as He Almighty said: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" [Az-Zumar: 53], and the Prophet, peace and blessings be upon him, said: "The one who repents from sin is like one who has no sin."

Repentance must fulfill its conditions and pillars. The rights of people require that they be fulfilled or that their forgiveness be sought. If fulfilling a right is impossible, one should give charity on behalf of the wronged person with the intention of benefiting the Muslims, and increase seeking forgiveness for those harmed by their tongue.

Indeed, abandoning prayer and disobeying parents are major sins. So, preserve your prayers, and know that disobeying parents incurs the wrath of the Lord. Increase in performing obligatory acts and supererogatory acts, hoping for Allah's favor.