how to delete photos from libra

You should be seeing "All Photos" in the toolbar, if Library is selected in the sidebar.

Like this:

If All Photos does not show, the Photos window may be too small, or you are in Full Screen Mode, with the toolbar and sidebar disabled. Then leave Full screen Mode and check, if the Toolbar is now showing All Photos.

If your Photos window is very small, drag the corners to enlarge it.

When you select some photos in "All Photos" the delete key ⌫ should suffice to delete the photos, also also the menu entry "Image > Delete" should work. Or is the "Recently Deleted" album too full? How many photos have you selected for deletion? Can you delete a photo, if you select only one photo or just a few?

Try starting in safe mode

How to use safe mode on your Mac - Apple Support

Also, where is your Library stored?

Great. You could also try the shortcut ⌘⌫