Is a brother who died in a car accident considered a martyr with Allah? And is what befell him good for him? And how can those affected by his death return to their lives and work? And does he hear and feel us when we visit his grave?

It cannot be definitively asserted that a person who dies in a car accident is a martyr. Knowledge of whether their death was good for them or not is with Allah. The Prophet, peace and blessings be upon him, said that a righteous funeral procession says, "Bring me forth!" while an unrighteous one says, "Woe to it! Where are you taking it?" and everything hears its voice except for humans. One must be patient and seek reward from Allah, for every soul shall taste death, and the greatest calamities after the passing of the Prophet, peace and blessings be upon him, become insignificant. Realize that life is a transient abode, and be like a stranger or a wayfarer. Take from your health for your sickness, and from your life for your death, for grief does not bring back an absent one. Strive in obedience to your Lord and seek the reward for your calamity, for Allah has promised the patient a great reward.