I don't do this to cause arguments. I do this because I'm a follower of Christ the Messiah and He told his followers to preach the gospel to all the world. I'm not good at talking to people in person so I take the easier way and use the internet. The easiest way I know to sum up the gospel is John 3: 16-21,
God loved the world so much that He gave His one and only Son so that whoever believes in Him may not be lost but have eternal life. God didn't send His Son to judge the world guilty, but to save the world through Him. People who believe in God's Son are not judged guilty. Those who do not believe have already been judged guilty, because they have not believed in God's one and only Son. They are judged by this fact: The Light has come into the world, but they didn't want light. They wanted darkness, because they were doing evil things. All who do evil hate the Light and will not come to the Light because it will show all the evil things they do. But those who follow the true way come to the light, and it shows that the things they do were done through God.