السَّلَامُ عَلَيْكُمْ shaykh May Allah bless you how should i revise after the lessons to retain the knowledge could you clarify this in detail Jazakhallah khair

Take it as a rule. The lesson itself is the foundation, and the notes and what to memorize are only aids, so never rely on them alone. Fix the knowledge by constant review and going back over it, by summarizing, and by writing and marking on the book itself, underlining and placing your own signs on it. Study through the week, and on the weekend revise everything you studied.