Speed Issues, Performance and Plugins

Hello everyone,

I have been experiencing very slow speed mostly in the admin page and sometimes loading the website. My web developer installed some plugins and the theme had some plugins. I called Godaddy to figure out what the issue is and they said that

“that you were also getting spikes in your hosting account’s resources. Typically, the issues you are noticing on your site are caused by either your wordpress theme or plugins.”

I searched here for info and I tried this website

https://gtmetrix.com/reports/www.revelationmag.com/d6aLUGIT

I have no clue what the first 7 problems are but what I want to fix right away is the
Serve scaled images

I downloaded the Ewww Optimizer and I bulk shrunk all the content but it there is still to be an issue ? any suggestions ?

As for the Plugins I Installed P3 Plugin Profiler
and it seems to be that the W3 Total Cacheis causing all the problem even though I thought it would help the website load faster!

Details in this image below
http://i62.tinypic.com/nq9zix.png

Did my web developer install it but not work on the settings or is this plugin not that good ?

If anyone have any suggestions on what I should install or delete or do please don’t hesitate, I have a beginner knowledge of wordpress so nothing too complicated please!

Thank you