How do I revise GCSE Chemistry/ Sciences effectivly

I'm in year 11 and I do higher triple and I don't know any of the content, to teach myself Chemistry I make notes while watching Cognito videos and from the specification but how do I actually revise it, I've tried online flashcards they aren't helpful and everyone say not to make physical ones as they are a waste of time/unhelpful and people say to do exam questions but I don't know how to do them as I don't know the content. How do I memories all the science content effectively to boost my grade from a 5- to 8 or 9?

Who is saying physical flashcards are unhelpful? Revision from one person to the next will be different, so even if a revision method doesn't work for a friend, it might work for you. It does depend on how you use flashcards, you need to make sure you are testing yourself with them and reviewing the flashcards you are getting wrong. I would take a look at spaced repetition to help memorise your flashcards. How were you using flashcards?
Making notes from videos will not be helpful because it is very passive, you need to make sure you are using active revision techniques (i.e. active recall).

I've tried making my own flashcards on Knowt but i found them unhelpful, and I've tried the ones on PMT but I also find those unhelpful. I'm trying to find a way to learn the content and revise it a the same time as I don't have much time left, so I was told that physical flashcards would take too long to make and would be a waste of time, so I tried online but they didn't seen to help me so I assumed physical ones wont help me either.

How are you using the online flashcards? Are you just reading them or are you actively testing yourself with them?

I tried to memories through them by going through them again and again but I found it difficult to actually remember anything

How are you going through them? Are you just reading through the flashcards?

Yeah

I'm in year 11 and I do higher triple and I don't know any of the content, to teach myself Chemistry I make notes while watching Cognito videos and from the specification but how do I actually revise it, I've tried online flashcards they aren't helpful and everyone say not to make physical ones as they are a waste of time/unhelpful and people say to do exam questions but I don't know how to do them as I don't know the content. How do I memories all the science content effectively to boost my grade from a 5- to 8 or 9?

I'm in year 11 and I do higher triple and I don't know any of the content, to teach myself Chemistry I make notes while watching Cognito videos and from the specification but how do I actually revise it, I've tried online flashcards they aren't helpful and everyone say not to make physical ones as they are a waste of time/unhelpful and people say to do exam questions but I don't know how to do them as I don't know the content. How do I memories all the science content effectively to boost my grade from a 5- to 8 or 9?