The best scenario for SEO is not to change URLs with a redesign.
Changing your url structure will definitely have quite an impact on your rankings because SEO traffic changes when URLs Change.
However, it takes time for the search engine to understand the new site structure to determine what is on the new version of the site.
All the intricate relationships between the pages of the site have been restructured, and this may take weeks or even months for the search engine to understand. In the meantime, they may feel a need to devalue your site somewhat.
Implementing 301 redirects from the old pages to the new pages will help with this problem, but it doesn't eliminate it entirely.
301 redirects just minimize URL change impact on SEO, but 301 redirects recover organic search performance after a short period of time.
You have to wait for your site re-indexing. It will take sometime.