SEO with Yoast Premium

I have a website www.greensolarsystems.co.uk and have just bought and installed Yoast premium

looking through things there are multiple errors for example readability, I am unsure if i should outsource rewriting each page (and additional work), my worry about the rewrite is if its not someone in the industry of solar systems will they be able to rewrite the current content in a better style.

The whole site needs overhauling and i understand that the Yoats premium will use AI for much of that i need to look through that and see if i can do that or if i should outsource it to save me time

Would you please look at the site and let me know your thoughts