Cant empty the trash can

Have you tried restarting your Mac and trying again?

 

Finder has to be open and active in order for the trash can to respond.

 

Important Question - Are you sure this was NOT one of the system folders? No system likes that and all systems will try to stop you. You simply may not have privileges high enough. Similar problem happened to me on Widows and I ended reformatting the hard drive.
If these are YOUR files: There are few more or less drastic methods which may help, but easiest and least dangerous may be restart computer in safe mode and try there. https://helpx.adobe.com/x-productkb/global/start-safe-boot-mode-mac.html
It should load minimum stuff in safe mode, so file may not be in use at that time. It is also worth checking the disk first from Disk Utility to make sure there are no underlying issues with the drive. And if nothing helps, it may be time to google the problem and follow some instructions. But when this happened to me in past, it was always challenge. Note, that when instructions tell you to become (and how) superuser in command line interface, you can do a LOT of damage quickly. Make VERY GOOD (and verified) backup first!

 

I have the same problem and I have not found a solution yet.

 

That looks like privileges issue. You should not be deleting someone else' home folder. The way that is done is by deleting the user from User management interface - at which point their home folder should be deleted. I remember fighting with similar issue at some point but do not remember how I fixed it.
If this was not home folder, but arbitrary folder in the system folders, it's even more tricky and one needs to get the privileges right. But that should be doable as superuser from command line. One can do a lot of damage that way.

 

sometimes a Force the Trash to empty using the Option key will work.

 

I‘ve had problems with ghost files a few times, very annoying. Usually, a process is using the file in question, although the file itself doesn‘t exist. There is a terminal command to find and stop these processes, but I use this free app https://sveinbjorn.org/sloth

It shows which files are busy and then you simply kill the process.