What is the way to get rid of the whispers of the fear of death and entering Hellfire, and the feeling of distress and lack of awe of God, knowing that one is committed to prayer and sometimes falls into sins?

Remembering death and fearing it and fearing the Fire is praiseworthy if it leads to preparation for the Hereafter, repentance, and righteous deeds. Fear of Allah is Islamically مطلوب (required/desired), and it is aided by reflecting on one's own shortcomings and the verses of warning, along with the necessity of combining this with a good opinion of Allah and hope in His grace. For Allah is more merciful to His servant than a mother is to her child, and His mercy precedes His wrath. Increase your contemplation of Allah's attributes such as Majesty, Grandeur, Mercy, and Forbearance, as this achieves balance between fear and hope, which are two essential wings in the journey towards Allah.