Safari doesn't load pages first time

Hello,

I have MacBook Pro Mid 2010, using El Capitan, Safari 9.0.2. There is problem to load web pages. Sometimes Safari load Facebook, YouTube or this Support Community immediately. But very often it doesn’t load for the first time, I have to open new tab, and try again, then new tab and try again and maybe for the fourth-fifth time it loads. Or it loads the web page after long time.

The loading bar just stops in the middle or I get the message, that something is wrong and page can not be loaded. This happens also when I type something in address bar and try to google the keyword. It just doesn’t load probably in 5 from 10 cases. It is really frustrating, because Firefox just load web pages with no problems. On my iPad and iPhone Safari works perfectly smooth. I do not use any plugins except Adblock.