Hello,
1) You built the site using the commercial version of WordPress. This version has its own built-in portfolio option https://wordpress.com/support/portfolios/
If you don’t want to use this then disable using the WordPress setting.
2) Our theme also has the portfolio option. To use our theme portfolio https://tempsderever.fr/notre-portfolio/ create projects under this portfolio item https://prnt.sc/15s62dz
Regards