Hey there hope you are doing well. Crash course is very important for the last moment revision and there are many crash course available in YouTube for free. The best according to me among all these is of unacademy accelerate - guardian of IIT JEE series.
They are solving questions and explaining theory e with the help of the questions and  are very good. if you are interested in theory as well so you can go for doubtnut crash course. There explaining theory very well. Hope this will help you good luck.

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