Hello !!
https://school.careers360.com/exams/west-bengal-12th

so..the provided link consists of important dates of examination,preparation tips ,examination pattern and sample papers which helps you get an preview about  question paper.And for some more question paper of WBCHSE ,you can find in the link below:

https://school.careers360.com/articles/wbchse-question-paper

Hope this would helps you.Do prepare well for the examination.