Being a Christian means you belong to the Lord Jesus Christ.
It means that there was a time when you turned to Jesus in faith. That means you trusted in His work on the cross as the complete and final payment for your past, present, and future sins, and you asked Him to forgive your sins and save you.
If you have done that, He has been faithful to forgive you and wash your sins away. That means He has saved you and given you eternal life.
Now you are free to serve Him. That means you get to know Him better through reading His word, attending church, and fellowshipping with other Christians.
Being a Christian is a positional standing. Acting like a Christian is another thing.