Hii Nitin

No it is not like you have to remember whatever you have studied in class 9th to continue them in class 11th . They are related but not completely the chapters are related as what you study in class 11th is a continuation of what you studied in class 9th and is more of an advanced version of the same . Don't worry you can study 11th even if you don't remember much of class 9th .

Hope it helps

Thanks