Will I be able to score really well in jee paper 2 If... I have already learnt the chapters but took 2 months to concentrate on boards

this question always haunts a class 12 student its natural believe me your board preparation will definitely help you in your preparation for jee paper.try to keep your class 12 syllabus strong and also pick those chapters of class 11 in which you are comfortable with don't go after those chapters of physics that demands a lot of attention and is time consuming. Class 11 chemistry is somewhat related to class 12 chemistry you can compile physical chemistry and hand to hand to revise chapters like sound and effects of sound in physics together. don't go after chapters like rotation and circular motion keep those chapters reserved for last time revision.

ensure that class 12 syllabus remains strong in your preparation.

all the best