Is it permissible to repair the elevator of a residential tower with Zakat funds, especially if some residents are not well-off, and is the money I provide for its repair considered charity (Sadaqah) or Zakat, knowing that I will complete the amount from my Zakat and pay on behalf of those who are unable?

The recipients of zakat (definition) are specified in the Holy Quran in the verse: "Zakat expenditures are only for the poor and for the needy and for those employed to collect [zakat] and for bringing hearts together [for Islam] and for freeing captives [or slaves] and for those in debt and for the cause of Allah and for the [stranded] traveler." It is not permissible to donate zakat to the owners' association for repairing an elevator or for other similar purposes, because the questioner himself will benefit from it.

However, zakat can be given to the poor and needy residents of the building to provide them with money, which they can then dispose of according to their needs. As for donating for elevator repair from sources other than zakat, with the intention of it being a continuous charity (sadaqah (definition) jariyah), there is no harm in that.