There are a lot of things that could cause your site to be slow.
The obvious of network speed, or not enough hardware (low ram, etc). You haven't specified your bandwidth or what you are running for hardware. You would want to check your server/network resource utilizations and see if there is a bottle neck there.
Database software and webserver software can be speed tuned. You haven't really told us if you have done anything like that. You would want to speed tune your software, and may need to allocate more RAM to processes, etc.
osTicket is a constantly changing piece of software. This means that you will need to keep it up to date. 1.14.6 is pretty old in the scheme of things 1.15.x has been out since Nov 2020 and is currently at 18.104.22.168 (released July 2021). Upgrading could fix the issues that you are reporting.
Lastly, what database format are you using? One of the Devs (Kevin) has posted several times here on the forums that they recommend converting all tables to InnoDB to improve performance.