I can't delete folder in trash

You must not manually delete items from a Time Machine Backup manually. That is why these items are permanently locked.

If you somehow DO manage to delete these items, they will, at best, blow a hole in your backup, losing some files from the backup SET permanently, and at worst make your entire backup SET unusable.

Time Machine manages these backups all by itself, and deletes the oldest backups when it needs more space. Your manual intervention is not helpful.

This pane spells out the algorithm used:

You can try to select the items and choose

Finder > File> Put Back

Or you can just ignore them, and leave them in the Trash. Eventually, Time Machine will remove them, after fixing all the links so that no files will be lost from your backup set.

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To keep a compact Backup Set, Time Machine stores only ONE copy of a file. If needed for a later backup (as of a certain later date&time), a LINK to the previously-stored file is created. Each backup (as of a certain date&time) consists of a few files, and a TON of links to previously backed up files.

To delete an old backup (from a certain date&time) Time Machine goes through all the files it contains, and carries the needed files forward, and updates the links.

If you just throw out a backup (from a certain date&time) you are discarding the ONLY copy of some files, and they are lost from the entire backup SET.

You should never attempt to delete Time Machine backups via Finder, they will always get stuck in the Trash as you found out. You'll notice if you disconnect the TM disk they will no longer appear in your Trash, but when you connect it again they will reappear. The easiest and fastest way to sort this is too erase your TM volume and start over.

This is one of the most comprehensive sites for Time Machine, I know.

http://www.baligu.com/pondini/TM/E6.html

It's author is deceased and it hasn't been updated but he suggests a method in that link.

The previous Time machine articles by the late James Pond are also available here, thanks to forum senior contributor Old Toad:

http://oldtoad.net/pondini.org/OSX/Home.html

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Yup, OT started hosting them at some point when the site wasn't being funded. Now both are up and running.