Every site has two speeds.
a) the speed a logged on user has
b) the speed a user who is not logged on has.
b) can be speeded up significantly by using a cache plugin. Cache plugins don’t do much for logged in users though so they don’t help with a) much. Also when you are logged on as admin they do even less which means that you will see the slowest time of all.
So decide what is important to speed up. If a), then all the advice about looking at wordpress internals, etc. is largely irrelevant because what the cache does is save the content as HTML and just display that and not invoke the php/wordpress/plugin/ environment and processing at all. It bypasses it. It is not used.
These are things to be aware of. Good luck with your site.