How to optimize page permalinks ?

Hello
I am using WP mainly as a CMS : let’s say the content is “vegetables”
Therefore my content is organized in the following way.

– HOME

— Potato
— Red potato
— Sweet potato
— yellow potato

— Eggplant
— Round eggplant
— L-shaped eggplant

My permalinks are :”/pagetitle/” so the search engine list my page as :
www. veggies . com / Potato / Red potato

BUT
red potato market is very hot, and I would rather have an URL like the following:

www. veggies . com / Red potato

(no level 1 menu displayed).

How can I do that ? I’ve checked plenty of websites, but they all give advices on how to modify post titles, and not page titles.

Thanks