Hello,
1) I’ve disabled Gutenberg and enabled WPBakery Page Builder for portfolio projects – https://www.8theme.com/demo/docs/legenda/Plugins/WPBakery_Page_Builder
http://prntscr.com/px9dqx
2) To change the URL, go to pages > edit your page that has template portfolio – http://prntscr.com/px9g76
Also, change translation of “portfolio” for the theme and Core plugin via Loco Translate –
https://www.8theme.com/demo/docs/legenda/Theme_Translation/Base_Theme_Translation
The child theme should be translated only in case you added custom code in child theme that includes localization functions.
3) Labels in the menu are images https://prnt.sc/pxfnzl You need to change images of labels in wp-content/themes/legenda/images folder.
Regards