I have accidentally deleted one folder from the Google Cloud Storage. How can I recover this folder?
You cannot recover from that:
Warning: Object deletion cannot be undone. Cloud Storage is designed to give developers a high amount of flexibility and control over their data, and Google maintains strict controls over the processing and purging of deleted data. To protect yourself from mistakes, see Deleting data best practices.
Take a look at the best practices documentation concerning deleting objects.
I cannot comment here but to complement Henrik Pingel's answer, there is an object versioning feature that would allow you to plan ahead of time against accidental deletion of objects, although it is not enabled by default, it is a good practice to enable it straight away after creating buckets.
We've got this after raising an issue through our paid subscription.
We would be happy to assist you in the restoration process, but as a caveat we're required to communicate with you that the restoration operation on Google Cloud Storage is done once per customer. Henceforth you (your organization by extension) won't be able to use the restoration process again. We would also like to mention that this is a very tedious process which has to be done manually and recovery of any deleted data is not guaranteed.
Don't store important data on Google Cloud Storage.