Hello Aspirant, Hope you are doing good.

I feel there is no need of studying class 11 again as you passed the class 11 and promoted to class 12 don't waste you time .

Try to work hard and attend the classes regularly and listen with concentration, ask your teachers , the concepts which you are unable to understand , study the basics of every concept. prepare a study plan and study accordingly , try to listen to concepts you missed on youtube or any other platforms which you feel comfortable. Don't waste time , study with concentration and practice the subjects.

Don't lose your hope. work hard.

All the best.