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Yes, the source for every Catholic is the Catechism of the Catholic Church. It's better to use the good old catechisms. For English-speaking Catholics, the Baltimore Catechism is very articulate. The Catechism of Pope Pius X makes clear the entire doctrine of the Church. So, you can use this and go there; this is a sure teaching of the Holy Church. So, you do not have to invent something, and this is the first.
Then, of course, there is the matter of living a prayerful life. So you must also pray and be consistent in your prayers. You cannot keep your faith when you do not pray regularly and intensely grow in faith. It is also necessary to receive the sacraments on a regular and frequent basis because the sacraments are the sacraments of faith, particularly the Holy Eucharist and confession.
I'd like to recommend reading Catholic apologetics books. So, Catholic apologetics are explanations of the reasons for our faith that will also help you. Some good dogmatic books explain well, such as Fundamentals of Catholic Dogma by Ludwig Ott. I encourage you to read good authors who defend the Catholic faith.