I love one Muslim girl from my heart since 5 years. I want to marry her but her parents don't know. My parents know and agree for me to marry her. Is it Sunnah to pray to Allah for her, to make her my life partner?

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 is His slave and Messenger.

If this girl is religious and good-natured then you may supplicate Allah to marry her. Islamic Sharee'ah urges people to ask Allah for everything as long as it is not a sin or to cut off kinship, even if it is a thong of a sandal. The Prophet said: “Let one of you ask his Lord for all that he needs, even for the thong of his sandal when it is cut.” [At-Tirmithi]

Therefore, you should take the legal steps to marry this girl by making a proposal for her to her guardian. Beware of having contact with this girl before completing the marriage contract, since such actions are contrary to the rulings and morals of Islam.

Allah knows best.