How can i crack iit jee in 5 months also with boards...... If i say that i have done only 20 % of syllabus.... Tell me the best way

Go and sleep itssss too late

See truly speaking it is quite difficult to study even for iit jee alone in just 5 months and you have to give board exams as well. So, what I suggest is that it will be better if you study lightly for your boards so that you can secure around 87% in CBSE and focus on just JEE main as you can get into NITs and also some reputed state government colleges. If you want to go for IIT you may try but it will be better if you give a 1 year drop and take coaching and prepare for jee advanced also you need to have a lot of patience while you are dropping so whatever you do do wisely. If you think you can clear iit jee after 1 year I would suggest you to drop.