Language GCSEs are tough but if you are determined to get a better grade and put in the time outside of lessons you will definitely see an improvement! At GCSE (and even A level) you definitely aren’t expected to be fluent, and for some bits like speaking and writing you can guarantee yourself a really good mark with some preparation.
What bits of the GCSE do you struggle most with? If it’s grammar (which I agree is tricky) you can go back to the basics of conjugation of regular ER/IR/RE verbs in the present tense, then memorise the conjugation of irregular verbs, then the imperfect tense etc and work from there. I’d recommend getting a grammar workbook for this as it guides you through all the grammar you need to know and has practice exercises to make sure you understand it and can apply it. Make sure you buy the right one for your exam board. I did Edexcel so I used the ‘Studio Edexcel GCSE 9-1 French Grammar and Translation Workbook’ by Stuart Glover.
Speaking and writing seem quite scary, but it’s the preparation that’s key here. You need to type up your notes for each theme and memorise the key bits for each theme and regurgitate these in your oral or writing. This can be time consuming, but even if you have a really good sentence or 2 for each subtheme you should be in a really good place. Our French teacher was really good at giving us lists of possible questions that may come up and giving us complex language to memorise to get those content marks, but I can see how getting good notes may be a challenge if your teacher isn’t as good. You could use your textbook, or ask friends from another class with a good teacher to send you their notes? Approach your teacher and ask if they can provide you with a rough list of questions that could come up in your speaking/writing and go from there. Also remember that for your writing you get a lot of marks for having mostly correct grammar, even if the content is less good, which is another reason for getting to grips with the grammar!
Reading and listening you can’t really prepare for apart from knowing key words for each theme (I think there are vocab lists at GCSE that you can go through and highlight the words you don’t know). The more past papers you do (available on your exam board’s website) and mark yourself, the easier they will get. Save most of them for Y11 though, and remember you can do past papers from other exam boards for extra practice. Listening I think is especially hard but I recommend searching up ‘Easy French’ on YouTube- they interview French people about day to day topics and have French and English subtitles on the bottom of the screen so you know what they’re saying.
Sorry for the information overload but I really think you can improve loads especially as you have lots of time! You’ve got this