السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللهِ وَبَرَكَاتُهُ whenever i study a lesson and move forward to another,it always feels like im missing something,i revise previous lessons again and again thinking i missed something i feel like i should memorise the whole lesson,how do i approach new&revise old

Never memorize the whole lesson. What is meant by attending the lesson is not that you know 100% of what was said. I myself don't know 100% of what I have said and explained in all of these lessons. What you need is to continue studying. Alhamdulillah, even if you understand 30% and what remains in your mind is as low as 10%, that is good enough for now. The more you progress and persevere for years, that 10% becomes 60% and 70%, and you start having grounded knowledge that is vast, insha'Allah. So persevere. The most important thing is that you never quit, that you continue to benefit, and that you continue to study and revise. Do not fall into a revision loop: keep studying, and just have a couple of days a week where you revise. That is enough, even if you do not retain 100% of the knowledge. Nobody retains 100% of the knowledge. Barakallahu feekum.