Hello Gaurav yadav

Yes you can score good marks in 12th class in physics and chemistry don't worry about the 11th class physics and chemistry which is not upto the mark as you told so don't even think about past please concentrate on the physics and chemistry of 12th class please study the ncert books and some reference books like for physics H c  verma and for chemistry please refer O P Tandon overall other preparation tips are follow the proper time table and refer the previous year question papers i hope you will get the good marks for sure 

Good luck