Q:

Auto update docker image if exist new version of images on DockerHub

I want to update and restart my application ( docker container ) when I push new version of this app to Docker Hub.
Can You tell any solution for auto update an image and restart them on server? 
P.S I hear about kubernetes, but its very hard to understanding how use it 

A:

There are lots of possibilities:

Write a poll service to look if a new version is uploaded and let it trigger a redeploy
if you have a private registry you might be able to add a trigger (notifications) to a new push. The trigger might trigger a new build.
if you let e.g. jenkins do the whole build it can also take care of the build and redeploy.
You can trigger ansible to do a redeploy based on a new version.
etc. etc.

