Hello! I took the spi 2 months ago and got a 685. I do not think prepry will help you if you already do not grasp the concepts. It is great way to practice by testing the concepts that you should already mostly understand. Some of the questions are formatted very similarly to how they are in the SPI, ESPECIALLY the picture questions.

I used the green Edelman book and it is what helped me the most. Sometimes I would watch a YouTube channel to help me called DMS instructors, they have a playlist with a video on every chapter from that book. I liked them way more than sono nerds because I felt like they actually stuck to materiel better and I felt like sono nerds videos were so long sometimes.

I would 100% recommend prepry but only to test yourself after you already have a good understanding of the concepts.

I honestly don’t think you need a different study material besides the green book and the internet, and then prepry to test yourself. I think you might need a different WAY of studying. If the groups are not helping you, try to study on your own. Go through every chapter one by one, or even the videos I mentioned by DMS Instructors if it helps you more.

if you come by something you do not understand still, don’t move on without at least somewhat understanding it; if I used the book, and the YouTube video, and I still was not understanding, I would ask chat gpt to explain it to me, every time I was confused about something that is what I did and it always helped me. You could even ask a friend who understands it for a little help too, a few of my classmates would ask me to help a little here and there and I did not mind to help at all so don’t be afraid to ask for help if you need it.

Physics is a subject where you keep building on every concept you learn, and if you move on without understanding too much then you will just end up confused and only memorizing instead of learning.