I assume you're talking about the edexcel grade 9 specific workbook?
If you have that one then yes you're probably fine in terms of resources(it's pretty much all I used) and I'm sure your school will provide many practice questions etc.
Don't worry about not being able to answer every question; in the workbook I could probably answer about 2-3/5 of every questions given because they were so difficult- they have to be in order to stretch even pupils targeting a grade 9. Often the questions are even ridiculous or convoluted but it's just a strategy to try and get you to practice weird and difficult questions with hard verbal reasoning etc. If you could answer all the questions already then what would be the point in even using it as practice to get better?
Most of getting better at answering difficult questions comes down to practice. Otherwise, just be logical and decipher the question. Think: what different topics have I learnt that can be applied to the question? Often you'll have to try different methods of working an answer out (like trial and error with methods, really) but this is natural and you will also become faster at selecting the right method with practice.
Most of all, you have to be confident in what you're doing. Work out every answer as if you're a mathematical genius, use every method as if you know it's the right one, attempt every question like you know exactly what you're doing and you have more chance of actually getting the right answer.
I got a grade 9 in maths