Are supererogatory acts taken to compensate for deficiencies in obligatory acts if they are only the Sunan of prayer, or does this extend to include voluntary fasting and Sadaqat?

Indeed, the first thing a servant will be held accountable for on the Day of Judgment concerning his deeds is his prayer. If anything is found deficient in it, it will be completed by voluntary prayers (Nawafil). Then, other deeds will be taken into account accordingly. The mercy of Allah Almighty is vast; He may compensate for deficiencies in obligatory duties with other good deeds, or with expiating misfortunes, or even without any action from the servant whatsoever.