Cannot delete locked folders and files that were shared to me years ago

Select the topmost folder and Get Info.

Click the padlock and Authenticate.

Click the + button and add your user with Read/Write.

Select your user, then select Make (your name) the owner from the ellipsis menu.

Then, select Apply to Enclosed from the ellipsis menu.

I you have multiple folders, repeat for each topmost folder.

Is your user Admin capable? I.e., is the "Allow user to administrate this computer" checkbox selected in Users & Groups for your user account?

If it is, Is that Dropbox the app/service of that name? The inability to access the folder is likely related to that program.

You can try using Terminal to change ownership with the following: You must do this as an admin user, so if that is the problem, this won't solve it.

sudo chown -R `id -un` ~/Dropbox/IIl\ Curso/ Corto\ Internacional

I'm not sure I spelled that correctly, so you may want to check. You can also just copy/paste all the way through `id -n`, leave a space, then drag the folder into the window. Hit Return.

sudo will ask you to enter your password. It won't show anything while you type.