Safari runs slow on macbook pro 13" (2015) and causes fans to run fast

I got my brand new macbook pro retina 13" (early 2015 model) 2 weeks ago and everything worked fine. Safari worked as usually but few days ago when I opened safari and tried to watch a youtube video my macbook froze and it couldn't load a simple video. I tried restarting it and did the same thing but it froze again and then fans started to run faster and the temperature (I use an app which shows the temperature of the macbook) got higher. The funny thing is that safari runs slow only when I open youtube, google and few other websites but for example apple.com, facebook and all of my mail websites work fine without fans running fast. I installed google chrome and everything worked normally but the problem is that chrome is not that comfortable for me to use and also I liked how safari worked but now I can't use it properly. What is the problem and how can I fix it?