Site running really slow

The site is version-1.5.6.4 and is using the Shoppica theme. It has 273 categories and 2500 products. The site takes up just over 2Gig in disk space. Pages were loading at an acceptable level, then started to load extremely slow resulting in error 503 pages. I'm new to Opencart and wanted to ask where do I start, in order to get the site back up to normal speed?

Thanks in advance for any help with this.

Well, post a link to that Site, if you plan to get a useful reply.
Ernie

Hi,
Sorry, I did mean to include a link - http://www.moette.co.uk/oc1/

Well, that really does not look good, the Google testsite even refuses to conclude the test:
Lighthouse returned error: FAILED_DOCUMENT_REQUEST. Lighthouse was unable to reliably load the page you requested.
Make sure you are testing the correct URL and that the server is properly responding to all requests. (Details: net::ERR_TIMED_OUT)
---
You have a lot of work ahead of you, to get this done, as it looks. And if you're not able to, PRO Support will be required,
to make this Site work, as it should, and probably could.
Ernie
---
https://developers.google.com/speed/pag ... k%2Foc1%2F
https://gtmetrix.com/reports/www.moette.co.uk/WFR0Tutl
https://tools.pingdom.com/#5b7536bbab000000
https://speed.devs.mx/analyze.php?url=h ... d=6640740
---

Thanks for looking into this, Ernie. In your opinion, would Opencart Lightning help with speeding up loading times, or would it be helpful to have a developer look at it? If the later is a better solution, any idea on cost?

Many thanks.

Well, you have fundamental Problems on your Site, and some of them cannot
be solved, just by use of an Extension like famous MaxD's Opencart Lightning,
but have to be fixed first, before even thinking about 'peaking' it up to it's best.

So, I really don't know, what or who to recommend, but you could send me some
FTP access info by private Mail, to have a first short and free inside view ...
Ernie