Is a young man considered devout or a hypocrite if he engages in a love relationship with a girl, while he is a Hafiz of the Book of Allah and leads people in prayer, and is it permissible for the girl to think of him and imagine him as a future husband?

You did well by cutting off conversations with the foreign young man, as they are a means to temptation (fitna). It is not permissible to converse with a non-mahram (definition) woman except out of necessity and within legitimate Islamic guidelines. A young man befriending a non-mahram girl is a mistake, a lapse, and a sign of weak faith. However, he is not described as a hypocrite merely for this; rather, he should be advised. Study may not prevent marriage, and if the young man is upright and you both are able to marry, it is a good thing, for the Prophet, peace and blessings be upon him, said: "Nothing like marriage is seen for two who love each other." If marriage is not feasible, continue to avoid conversation to prevent temptation, and seek Allah's help in strengthening your faith. Imagining the young man as a husband is permissible as long as it does not lead to something forbidden.