Authority and competence comes from practical experience. Many people have knowledge of the Bible but they do not know Jesus Christ, they have NO AUTHORITY. You can only speak with authority about Jesus Christ if you KNOW Him and if you follow Him every day.
There are many Bible teachers and preachers who have NO AUTHORITY because they don't know Jesus Christ. Many know the Bible well but they don't know Jesus. Your COMPETENCE, our AUTHORITY comes from KNOWING Jesus Christ through our relationship with Him, walking with Him every day.
Do you KNOW Jesus Christ? Do you FOLLOW Him and OBEY Him? Do you KNOW His VOICE? Do you have a TESTIMONY? Can you speak with AUTHORITY or do you talk what you do not really know about? Our competence is from our relationship with Jesus Christ. How competent are you as a child of God? Do you really KNOW Him?
May Jesus bless you.