While deepin OS is based on debian (unstable), it would seem that installing the deepin desktop environment (DDE) is not supported. As far as I can see, there are no pre-compiled repositories for debian for easy installation. There is however support for other distros such as Ubuntu and Manjaro with repositories as detailed on Desktop Translation deepin page.
It might be possible to build all the packages related to DDE on your debian system. However, this could result in a broken system due to dependencies and other packaging issues.
I would therefore suggest switching supported distros if you are adamant about using Deepin as your DE. An alternative to this is to run Deepin OS or similar within a local VM. This will allow you play around with the deepin DE that is isolated from your main debian system.