Slugs of post types like Portfolio, Albums, Team can change from The7 > My The7 > The7 Post Types and Elements
For other post types like Testimonials, Benefits etc please try this method.
To change post type category slug try this method.
We do not suggest to name it simply “portfolio”, because in case you have any portfolio items or page also named “Portfolio”, it will cause a conflict between the name and the slug.
When all is done, go to Dashboard -> Settings -> Permalinks and hit the “Save” button.