All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu`alayhi wa sallam, is His slave and Messenger.
A man is not allowed to imitate a woman’s voice, either in singing or by means of joking, since this is considered an act of imitation that the Prophet has prohibited. In his Saheeh, Imam Al-Bukhaari narrated that Ibn ʿAbbaas said, “The Messenger of Allah cursed those men who are effeminate, and women who imitate men.”
If the singing that you learn is accompanied by music, then it is prohibited since Muslim scholars unanimously agree that singing accompanied by musical instruments is unlawful and thus should not be practiced or even heard by men and women alike. The list of scholars who reported such consensus on the prohibition of instruments, except Ad-Duff (i.e. tambourine), includes Imam Al-Qurtubi, Abu At-Tayyeb At-Tabari, Ibn As-Salaah, Ibn Rajab Al-Hanbali, and Ibn Al-Qayyem .
In the same vein, if singing is not accompanied by music yet its words are ugly and call for vice and immorality or describe women or wine, etc., it is also forbidden.
Allah knows best.