Hey Deliopk,
I will cover the issues in the same order:
1). Changing the slug base of the portfolio tags is not envisaged as a back-end theme feature, yet you can do it by customizing the code (I would recommend that the person implementing the changes has a decent knowledge of php):
– in the “functions.php” file, line 409
– in the “header-functions.php” file, lines 231, 267, 357, and 369.
2). The wider box appears because evidently you’ve chosen a tag archive page as your front page; the box is the tag archive info section, as envisaged by the theme’s templates. In order to remove it, you’d need to remove the HTML element with the ID “portfolio-header” from the template file which controls the page that is being rendered (I could suppose it is “taxonomy-tagportfolio.php”, yet I can see by the body classes that it might be a custom template as well.
Sincerely,
Andrii / Satori Studio