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, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
May Allaah The Almighty reward you for your keenness on calling people to Islam. This shows how much you really love Islam and care for Da‘wah. However, you have to know that talking with non-Mahram men has certain restrictions and limits that should not be exceeded, even if it is for the sake of Da‘wah. Among those restrictions are:
It would be better for you to look for any of your Mahram men or any Muslim man to do this task instead of doing it yourself, so that you would preserve your religion and avoid any bad consequences that might only be realized after it is too late.
If you could not find any one to help you, you can resort to the cassette tapes or CDs in English or in his own language (if available), the interpretation of the meanings of the Quran, and introductory books that give general information about Islam. All this is available in bookstores and most Islamic centers.
You can also make use of some websites on the Internet which broadcast the teachings of Islam in English or in his language. We pray to Allaah to guide him to the right path.
Allaah Knows best.