Dear Mr. KHAN,
I am interested in this project. I have experience in fixing these issues in my recent Magento projects.
It can be the following reasons,
* Multiple Crons were running (Duplicates)
* Slow queries from third party module
* Flat table not enabled for catalog
* Low memory for elasticsearch
* Poorly written code in module and theme
* Varnish, Redis not configured
* Images were not optimized
Looking forward to hearing from you,
Thank you,
Kind Regards,
Chandirasekaran