Why is the site loading slowly?

Question

Drupal

Hello.
Faced a problem. There is a site on Drupal and the site loads very slowly, sometimes there is a delay of more than 1 minute, or even it does not load at all!
I used some kind of service that diagnoses what exactly slows down. It was written there that it was necessary to "combine" JavaScripts files into one file, saying that it would be easier for the site to access JS.
But I did not combine anything, maybe this is not the problem.
I had options:
1) a problem on the Hosting. Perhaps their server is weak, it may make sense to switch to another Hosting;
2) in the root folder of the site there are files that weigh 15+ GB. Could there be a delay in loading the site because of this? The site itself weighs ~30 Mb;
3) there are a lot of installed modules in the CMS (most of them work), maybe because of them there is a problem;
4) a problem with JS scripts, they take a long time to load;
5) Yandex.Metrica works on the site, I think it affects the site loading.
The site loads quickly at night, and during the day it is very bad.
Please point me in the right direction to find the problem.
Thanks in advance!

Answer 1

one)

hosting problem. Perhaps their server is weak, it may make sense to switch to another Hosting;

Check with your hosting provider which SSD or HDD is being used. And if the site has good traffic, then you need a server, not hosting.
2)

in the root folder of the site there are files that weigh 15+ GB. Could there be a delay in loading the site because of this? The site itself weighs ~30 Mb;

As the most banal option - temporarily delete these files and check the site's performance, and decide on this option. Whether he had a reason or not.
3)

there are a lot of installed modules in the CMS (most of them work), maybe because of them there is a problem;

There are sites that show the loading (their speed) of specific modules. Try to check. It is trite to look through any browser loading of this or that element on the site - the developer panel will help you with this, or rather the web console.
4)

problem with JS scripts, they take a long time to load;

First, try to compress them. Most often, optimization helps.
5)

Yandex.Metrika works on the site, I think it affects the site loading.

I doubt it, but again, the web console will tell you this.

Answer 2

In any case, a minute of loading is a sign of serious problems. They need to be dealt with by experts. You, most likely, do not belong to them, so you will not pull.