I can do training on Resolve myself and have a couple of videos about editing in Resolve you and watch for free. But there are a lot out there and below are a couple of recent tutorials produced by other people in which you may be interested.
There were a couple of webinars recently on Moviola.com which you can view for free, as recordings. They are entirely based around the editing side of Resolve. I have used Resolve 15 quite a bit but I still did learn a few things. You probably have to know a little bit about editing generally, so this won’t help a complete beginner, but if you are used to Premiere or EDIUS you will appreciate being shown the Resolve way of working and learning some of the different things it does. You can view them here: https://moviola.com/webinars/craft-editing-davinci-resolve-15/
Ripple training has released a video pack on the new features of Resolve 15, which is available to but for $79, but if you use the discount code new-resolve-15 you can get it for about $55.
The author is the person who writes the manuals for Resolve so he should know how things are supposed to work. I find he speaks a little slowly for my tastes so I choose to download the tutorials and play them at double speed in VLC.
These tutorials are for people who know Resolve and are just trying to find out all the new bits. You can read more here: https://www.rippletraining.com/products/davinci-resolve/davinci-resolve-15-new-features//