Hello from Germany,
I used to be a Mormon. In fact, I was once a missionary, exactly like the young men you spoke to. I used to approach people with my mission companion, discuss the Bible with them, hand them a copy of the Book of Mormon, and invite them to view church films. Their intent is to convert you, no matter how nice they are (and Mormons are very nice). When I was a missionary, I received specific guidance from leadership not to invite teenagers and children to learn more about the church without first obtaining parental permission. You should definitely share this with your parents and ask for their permission before you do anything. Having said that, odds are these missionaries are just as I was - knowledgeable in what I was taught to me by church leaders, teachers, and parents, but completely ignorant about true Christian history and the actual origins of Mormonism. The official story taught in Mormon churches, which the missionaries take to the world, is a carefully-packaged whitewash of what really happened historically when the Mormon church was founded. They also won’t tell you about some teachings you won’t find out about until after you become a member or conduct some research by yourself (for example, polygamy; denying men of African ancestry the priesthood; the idea that you, Satan, and Jesus are spirit siblings, living together with God as spirits in a pre-earth existence). So, I advise caution. Definitely, talk with your parents first. The missionaries should not take you to the local church for a film without your parents’ knowledge and permission.
NS