Website tremendously slower since transfer from sub-directory to public_html

Hey guys,

I created a sub-directory (www.stampthewax.com/-) of my main domain (www.stampthewax.com) so I could design a new site whilst keeping things running as normal on the main domain.

One I had finished designing it, I transferred the sub-directory into the public_html, changed the home and site url path configuration in the wp_options table using PHPMyAdmin (from https://www.stampthewax.com/- to https://www.stampthewax.com) and then went into WordPress settings and changed the WordPress Address (URL) and Site Address (URL).

Everything seems to have changed over quite smoothly (except weirdly random photos had to be re-uploaded). Anyway, ever since I made the transfer my website speed has dropped a giant amount I have no idea why!

I went on https://gtmetrix.com and it has dropped from say 97% to 65% which you can see here: https://gtmetrix.com/reports/www.stampthewax.com/6yRSghYu

Gtmetrix says the main problems are:

Serve scaled images
Specify image dimensions
Leverage browser caching
Prefer asynchronous resources
Defer parsing of JavaScript
Add Expires headers
Make fewer HTTP requests
Use a Content Delivery Network (CDN)
Avoid AlphaImageLoader filter
Use cookie-free domains
Reduce DNS lookups

I’m a complete rookie so have no idea about most of these things. It seems to me that since it was so fast before hand and since the transfer there are all these problems there must be something I did wrong along the way or haven’t done yet which is crucial.

I read something about caching but again, don’t really understand where to find that.

Any help would be greatly appreciated,

Best,
Jo