Is it permissible to repeat the Istikhara prayer for the same reason? And what is better: the Istikhara prayer, the Witr prayer, or the regular Sunnah prayers? And when is Istikhara prescribed?

Istikhara prayer is prescribed when one is hesitant about performing a permissible act. It is not for obligatory acts, recommended acts, prohibited acts, or disliked acts. It consists of two rak'ahs, not from the obligatory prayers, and should be performed outside of disliked times for prayer. One then recites the Istikhara supplication. The supplication can also be recited after any prayer. The Witr prayer is superior to the regular Sunnah prayers and other supererogatory prayers.