Hello and welcome Lagarde. I was a former Protestant Christian and my father is a Protestant pastor. I became interested in Buddhism when I was 17. I was a Mahayanist for 1 year before starting to study Theravada. I chose Buddhism because it is the only religion that provides a permanent solution to suffering.
You know that as Christians we seek the eternal life promised by Jesus. Just accept Jesus as our savior and all our sins will be forgiven. If we refuse we will not have the right to eternal life, but to hell. When I saw that Lord Buddha said that even the pleasures of heaven and the sufferings of hell are not eternal it was a shock. I had also learned that we are our own saviours.
Lord Buddha is only a guide and not the one who will bear the burden of our bad deeds. It shows that the final solution to all this suffering is to stop desiring the things of this world and to understand the true nature of this world. Theravada is the Dhamma and it is the school which best represents the Triple Gem (Buddha, Dhamma and Sangha). Other schools have complicated things and added elements foreign to the Dhamma.
To develop confidence in the Dhamma, you need to hear explanations from a person who is at least sotapannā i.e. a person who has fully understood the basis. You can read the suttas on your own, but you need someone who has fully understood it to explain it to you and help you understand what you have read. We call that noble friend, in Buddhism. After this, you will become a sotāpanna yourself and your confidence in the teaching will be unshakeable.
You will know how to share it when your confidence is unshakeable. However, I suggest listening to sermons from monks who know how to talk to non-Buddhists. Jethavaranama Monastery is very skilled in this field.
See these sermons to get an Idea :
This website uses advanced Dhamma terms. I share these sermons because they are excellent for beginners. Of course, you can jump straight to this website and learn.
You have the option to have a Zoom call with the monks at the monastery. Let me know if you’re interested! :)