Please try the first answer of the following thread and try if it works then:
https://bbs.deepin.org/post/146414

I think you can try the method  nipos have shared:
" The problem are the servers.
They are all in China and access to them isn't that fast in countries which are far away from that.
I'm in Germany and I have the same problem.
If you use the apt-get command line tool instead of the graphical store,it can be fixed very easy.
Run the following command: sudo gedit /etc/apt/sources.list
Now replace the Mirror URL (beginning with http:// and ending with the first space after the http://) with the one of the mirror nearest to you.
You can find the list here https://www.deepin.org/en/mirrors/packages/
Now save it and use the fast apt-get
It is very unlikely that this will work with the Deepin store,too.
I think it doesn't use the specified mirror but their own servers which are all at one location."