That it up to God and the person you are sharing the faith with. Your role is to present the truth of the Catholic faith with love and clarity. You must remain focused on the role of planting the seeds. You may not be around to see if that seed grows, but you know that you have done your job if you explain the faith clearly and with love. The rest is up to the Holy Spirit.
Conversion usually takes a long time.
All that you can hope for is that you have planted a small seed that may bear fruit in the future. If you simply correct one misunderstanding or make one good point, then you have succeeded. Make sure you keep this from happening by diving the time equally and asking your own questions. No, it is not sacrilegious to write in your Bible. By highlighting verses and writing notes in the margin, you can save precious time finding key passages.