To speed things up there are a number of plugins you can install temporarily to clean your database and remove revisons that Wordpress creates automatically. There are also plugins that cache your content as pure html. You can experiment with these and see if the advantages of another such plugin outweighs the drawbacks of yet another plugin but as a rule I would only use plugins that are essential.
A dedicated Wordpress hosting service, I am told, can increase delivery speed.
‘Ahrefs’ is primarily an SEO tool but it is great for analysing individual page delivery speeds.
Using a free service such as Cloudflare can increase performance by caching pages and since many people use Wordpress, the large CSS and JS files it uses may already be cached.
Look at identifying exactly which pages are slow and why and then address those issues directly.
I hope these ideas may help.