Hi arshiamoghimi77...Bring up Deepin Store and in the upper right corner there is a little down arrow and click on it.  A little window will appear so then choose the "reference" option. A bigger window will appear and on the left side choose "Mirrors".  Then on the right side in the upper corner there will be a rectangle shape box that says, "Select the best mirror".  Click on this as this will pick the fastest repositories in your area.

Hope this helps you.