MacOS – Unable to delete Dropbox folder from the local hard disk

I have installed Dropbox app on Mac. This created a folder named "Dropbox" in my home folder.

I copied a large folder into this Dropbox folder.

The syncing of this folder is taking a lot of time so I have unlinked the Dropbox folder from Dropbox app (Dropbox app preferences -> Account -> Unlink the dropbox). Now when I try to delete this "Dropbox" folder I get the below error:

  The operation can’t be completed because some items had to be skipped. 
For each item, choose File > Get Info, make sure “Locked” is deselected, and then check the Sharing & Permissions section. 
When you are sure the items are unlocked and not designated as Read Only or No Access, try again.

I have seen the 'Get Info' and see that the folder has 'locked' checkbox not ticked and also in users I see that I have read&write access

I also restarted my Mac but I still get the same error

How do I delete this folder(including all its sub-folders). How can I force delete this folder?

I am able to move the folder to Bin but I cannot delete the folder from Bin. I was doing 'Delete immediately' option and the folder is not getting deleted. How do I get the free space on my hard drive back?