Here is your GTmetrix report:-
It shows the page being 1.55BM which is not hugely over the top by today's standards, but the load time says 20.2 seconds which is quite poor.
It looks like the issue is the sheer number of requests.
The "waterfall" there is a good place to spot bottlenecks.
It's showing lots and lots of little requests happening in serial which is taking all the time.
Perhaps combining some external resources like js and css into a single or at least fewer files would benefit you.