what will happen for year 2021 syllabus will be reduce or not and how much??

Harshit, we do understand that you are an Engineering Aspirant. If you are asking about JEE Mains, then yes. The MHRD did inform that the syllabus for both JEE Mains and NEET will be reduced for the year 2021 as the Academic year has been reduced due to Corona pandemic. The MHRD has not yet officially announce the syllabus but has requested suggestions regarding the topics that can be reduced for the Academic year 2020. Now if you are enquiring about Board syllabus, there is no official information about it. And if you are preparing for appearing for JEE Mains 2021, we would suggest you to stick to NCERT books for now instead of buying any book. Not atleat until NTA releases the official revised syllabus. Because no body knows what the reduced syllabus is. So instead of buying various books available in the market, you should stick to NCERT books and prepare from them regularly. Once the official syllabus has been announced, then you can start preparing accordingly and purchase books. But now will be too early.