Can I buy more storage for my MacBook Pro?

The current Macbook Pros do not allow upgrading the storage nor the RAM.

If you are within 14 days of purchase, you can return it "No Questions Asked", and buy a different model. If you are in that window, do not delay.

If you are beyond the 2 weeks, then it will be up to the descression of the Apple Store manager, but chances are they will say no, but you will not know unless you ask.

If a return is not an option, then a different approach is to pay for additional iCloud storage and enable "Managed Storage" where macOS will move files to iCloud but keep a pointer to the iCloud storage and when you try to access a file that has been moved to iCloud, macOS will download it via the network.

<How to free up storage space on your Mac - Apple Support>

<https://www.techradar.com/how-to/computing/how-to-manage-storage-in-macos-sierra -1329386>

That depends on which Mac you own.

If you post the

Apple menu -> About this Mac

Information, someone will be able to help you