How can I help my friends who are going through existential questions and doubts about Islam, given that I am not qualified to do so, what are the reliable sources I can recommend to them, and how can I convince them when they are my age?

Engaging in dialogue with friends requires knowledge and patience. Therefore, one must begin by equipping oneself with beneficial knowledge and righteous deeds.

It is essential to focus on reading and reflecting upon the Holy Quran. Among the recommended interpretations are Sheikh Al-Sa'di's Tafsir (Tayseer al-Kareem al-Rahman).

As for reliable sources suitable for this age group, they include: "Atheism for Beginners" by Dr. Hisham Azmy, and "The Quran and Your Existential Questions" by Dr. Mohab El-Said.