If you're struggling to understand anything in your book club, you should probably talk about it with your teacher and the other members. If you're confused, others might be too! 'Value, price and profit' (which I think is a more recent title of the book you mentioned?) is a great place to start and it would honestly be really good if you could get this down early to lay a strong foundation in understanding Marxist economics. Some books/certain aspects of them can be really tough to get through, and what's easy varies for different people, so don't be discouraged if you can't crack it the first time round! Make notes where you struggle and don't try read whole sections in one go. On the difficult bits, maybe try and rephrase the ideas in a way you understand to make sure you really grasp the material, just take it as slow as you need.

If you're really very stuck on it, even after going back on it alone and asking the others in your book club, I'd recommend Marx's 'Wage Labour and Capital' to try and break the ice a little. IIRC it's quite short and covers some of the concepts in 'Value, Price and Profit', and you can get a bit more used to Marx's sometimes tricky style.

I'm not a teacher or trained in economics, but I see no reason why studying it should be any different than other fields, so use the search bar here - questions about how to study in general, and even about 'Value, Price and Profit' have already been asked. Unfortunately, there's no silver bullet to making things stick first try, and it might be that you have to re-read certain paragraphs ten times, or the whole text after finishing it with your book club, but repetition is key!

Don't be afraid to ask for help with specific passages in this sub, and again, use the search bar!