What do you mean dead videos, are you talking about not having views? Revitalizing older videos can be hard, have you thought about rebranding your newer content?
Trying linking your older vids in the description or in the video. It'll give people a reason to keep browsing you channel and look at your older content.
To be honest, I'd adjust your lighting in your videos because I can barely see what you're doing most of the time. I'd also lay down on the tags YouTube's algorithms aren't CaseSenSitive so you don't need to add 500 different versions of the same thing. If you need any more help with descriptions and tags and how to use them effectively check out his tutorial
-> https://creatoracademy.withgoogle.com/creatoracademy/page/lesson/discovery?ytref=popular&hl=en
As a couple mentioned above working on the description, adjusting the Title, the tags and using info cards in a new upload with a link to your old video are things to breath back life into it