Slow Website after installing WordPress

Dear WordPress Community,

I am writing to receive some support on a speed issue regarding the website of the organization I work for:

http://www.nycnvc.org

Please note I am not a web developer so excuse the ‘lay’ terminology at times. We migrated to a WordPress site about a year ago, and since then access to the website has been painfully slow (pages take several seconds to load). We verified that this does not relate to our server host (DirectNIC).

Rather, after some inspection, we believe that part of the time lag is due to the creation of the webpages themselves: indeed, when viewing the source page after loading the home page (or any other page), we noticed the last two lines of the code being:

<!– Dynamic page generated in 3.583 seconds. –>
<!– Cached page generated by WP-Super-Cache on 2017-01-17 15:44:58 –>

For further confirmation, we saved such page and then statically requested it from a different address, and loading is immediate in this case, once all libraries, styles and images are loaded in cache.

Could you please provide some support on how to solve the issue? Is there some setting on WordPress that needs to be changed so that the pages are not recreated dynamically every time?

Your help is much appreciated, working on the website has been quite challenging with such slowness.

I look forward to hearing from you.

Clara