If you cancel your Premium Subscription, it will only cancel the auto-renewal.
You will keep all of your Premium features until the subscription expires. Once it expires, your account will revert back to a free account and you will not be charged again unless you re-subscribe.
You will not lose any of your Projects, only the Premium Features that you had.
To cancel your Premium Subscription, from your Avatar menu on the top right, go to:
My Pro Account > Manage subscription > Change Subscription > Turn off auto renew
Note: For Studio accounts and Recruitment accounts, it is the same process.