Hello,
Thank you very much for choosing our theme and for contacting us.
1. Please save your translation file in wp-content/languages/themes/bsel-pt_PT.po folder.
2. Please read and follow these suggestions in the process of update https://xtemos.com/docs/basel/faq-guides-2/4-x-5-0-migration-guide/
If the problem with the menu remails, please restore the site from a backup and provide your site admin access to the private area.
Best Regards
Best Regards