I posted this similar issue on reddit before. I contacted Siteground support and this is what they said:
Hi Muhammad,
Here is a link detailing how you can review the Raw Access Logs to learn more about incoming requests:
https://www.siteground.com/kb/find-website-raw-access-logs/
Reviewing the logs, the resource usage is caused by excessive WP-Cron and AJAX executions generated by the website application for (our site)
I suggest you replace WP-Cron with actual Cron jobs, which can be setup as per the following guide:
https://www.siteground.com/tutorials/wordpress/real-cron-job/
Here are links detailing how you can find which components of your web application are responsible for AJAX executions and how they can be reduced:
https://docs.wp-rocket.me/article/985-how-to-find-which-plugin-calls-admin-ajax-php
https://www.webnots.com/fix-slow-page-loading-with-woocommerce-wc-ajaxget_refreshed_fragments/
https://my.siteground.com/support/tutorials/wordpress/limit-heartbeat
Additionally, site is being bombarded with requests from Google and Facebook . We recommend you to drastically reduce the GoogleBot
crawl rate . Here are links that detail how this can be done: https://developers.google.com/search/docs/crawling-indexing/reduce-crawl-rate https://developers.google.com/search/docs/crawling-indexing/pause-online-business https://developers.google.com/search/docs/crawling-indexing/large-site-managing-crawl-budget#improve_crawl_efficiency There is also a lot of traffic from "facebookexternalhit" bots which can be very aggressive. They typically start scraping your site when someone posts a link on Facebook. If you're aware of any ongoing campaigns on Facebook, you may want to temporarily pause them. For more information on their bots, check out their documentation (and/or their support team): http://www.facebook.com/externalhit_uatext.php If you wish to block these bots, you can add the following rules to your websites' .htaccess files :
SetEnvIfNoCase User-agent facebookexternalhit not-allowed=1
Order Allow,Deny
Allow from ALL
Deny from env=not-allowed
Please note that Facebook will no longer be able to scrape your website pages if you do this.
I would recommend carefully reviewing your website apps settings to reduce resource usage as quickly as possible.
So, can anyone help me with how exactly I can fix these issues on my site?
I mean they gave you a comprehensive set of steps to follow. Just read the linked articles and start implementing them one by one. Take full backups before changing anything.