How to determine the reason for the slow operation of the site?

Question

stress testing

Good afternoon.
Condition: There is an industrial equipment store 1prof.ru . Both the external directory and the admin part work extremely slowly - delays up to 15-20 seconds.
Question: How to determine the reason for such a slow operation? Potentially, this is either a bad hoster or a slow engine (used by WebAssyst, old version). Also, there may be trouble with the local Internet provider (suddenly the site is dumb only from the office, although this is unlikely).
I would be grateful if you look at the site from the outside, and make reasonable suggestions how to fix this.
UPD:I checked the loading speed of the site, it is 3 to 10 times slower compared to regular stores, including even heavy Ozones and others - about 20-30 kb / s (main page). How normal is this?

Answer 1

I would suggest newrelic . To monitor the performance of individual parts, that's it. A free subscription is enough for you. Moreover, for the first month they give a full subscription for use.

Answer 2

I checked with 2 different providers, delays are 1-3 seconds

Answer 3

For more detailed diagnostics, use the webmaster tools: Google PageSpeed ​​Insights and Yandex.Metrica <monitoring: page load time>.