Hi Rajat,
I have answered a similar question a few days ago. You can find it here: https://www.preplounge.com/en/consulting-forum/bcg-paris-round-23-advice-for-written-case-1063#a2050
My recommendation is to prepare on practice material by timing yourself (to make sure you can cover all the questions within the allowed time).
You will find a couple of written cases here:
https://www.dropbox.com/sh/tqrn34hddrpg696/AABCpypFAmyaWEFSCFGIDpafa?dl=0
You can probably find some additional preparation material on this forum as well.
Once you have finished the exercise, I highly recommend you to share the outcome with a peer (even better if you know an experienced consultant) in order to get his feedback and exchange/get challenged on the content.
Good luck,
Jacopo