Before you can defend the faith, you have to know it. Peter tells us to be ready to give a reason for the hope that is in us (1 Pet 3:15), and Jude calls us to contend for 'the faith that was once for all delivered to the saints' (Jude 3). You cannot contend for a faith you cannot describe. Most of the confusion you will meet on the doorstep or the street is not about evidence at all but about what Christians actually believe.
This module walks through the great doctrines of the Christian faith as the Reformed churches have confessed them: Scripture, God, the Trinity, the person of Christ, humanity and sin, the work of Christ, salvation applied, the church, the last things, the covenants, the Holy Spirit, God's law and worship. Each lesson builds the doctrine from Scripture, shows how the church came to confess it, gives you the precise vocabulary, quotes the historic confessions and catechisms, and notes where other groups in this course depart from it. Where Bible-believing Christians differ (Calvinism and Arminianism, baptism, the millennium, spiritual gifts, the Sabbath, worship), the module states the Reformed conviction, presents the other views fairly, and shows what unites us.
Treat this module as the foundation under everything else. The goal is not just to win arguments but to know and love the God you are speaking about.