All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Indeed you did well by being keen on spreading Islam and calling people to it. This should be the activity of every Muslim. May Allaah reward you for your endeavour. You have to know that having friendship with a non-Muslim within the context of loving him and being an ally to him is forbidden. Allaah says (which means): {And if any amongst you takes (disbelievers) as Auliyah (friends, protectors, helpers), then surely he is one of them.}[5:51]. However, you should treat him kindly. The best kindness that a Muslim could have to a non-Muslim is to call him towards Islam and to show him its bounties and blessings, mainly in the field of relationships and good moral character. Nonetheless, there is no harm on you to continue calling this man to Islam provided you expect him to become a Muslim, you are safe of being affected by him, and you have enough religious knowledge to repel his misconceptions. If you lack one of these conditions then it is an obligation on you to end this relationship with him to be safe about your religion.
Allaah knows best.