Site loads without theme in the first load-Page Not Found when update or publish

Hello. I got a problems with my WordPress site gubkin.edu.vn
1. In the fist time loading the site, I get It’s without theme. I have to load the second time to have it in right format.
2. When I sign in the admin site, I often get trouble with “Page not found” when update or publish posts or pages.

Is there anybody can help me, please!.