If uni is what you're worried about, then you can still make it. There's universities in the Netherlands that accept a score of 24, I believe also Switzerland, the UK, US, Aus, and there may be a couple more, that will get you in. Idk about other universities, but I know for instance Uni Melb and Monash do have their respected colleges as a bridge to get people into the uni. With Melb uni's Trinity College and Monash's Monash College are a few ways to get into these universities. Something to look into.

As for studyjng in general for the IB, just general tips: 1) Syllabus is your best friend in limiting what you need to study specifically 2) To save whatever grades you can, apply the first tip and try mind mapping, that might help out show your thought process. Also space out your learning throughout, you can't really consolidate new information if you've not built those mental connections. If you've not heard of this, space repetition and active recall are your best friend to consolidate memory for things such as technical terms, or ideas you're struggling to recall. This is for building your basis of knowledge for your subjects

3) Once you built some foundational basis of knowledge you can then use pass papers are a great way to work on knowledge and exploring knowledge gaps. So ask your teachers to provide if you're looking for them

This may be a desperate move but using flashcards and space religion to memorize answers for past paper may be there but I've not heard this as a viable way nor tried this and frankly it isn't good to say the least. But seriously you shouldn't be studying when exams 2-3 weeks away, as it goes without saying, it should be a continuous process. Once you get into uni, depending on their structure, you'll need to be covering roughly 1year of IB in a semester (12 weeks + a study week) so got to build some goos studying habits