Payel, you can visit the official website of CISCE to get the last years' question papers of ISC 12th board examination of all subjects. You can visit the link: https://www.cisce.org/downloads.aspx You will have a heading as 'ISC Question Papers' which has the previous year question papers for the years 2019, 2018 and 2017. You can download the zip folder which has question papers of all the subjects, including Bengali. You can make use of it to understand the question pattern and prepare for your exams. All the best.