As soon as a theme displays a menu in the frontend, you have the option of defining it in the backend as well. However, the procedure varies depending on the theme. For classic themes (such as Hueman), this is done under Appearance > Menu. For modern block themes such as TwentyTwentyFive, it is done under Appearance > Editor > Navigation.
Since Hueman is a classic theme, you should have defined the menu under Appearance > Menu. What do you have there? Have you also checked the menu there as the main menu (check mark at the very bottom when editing a menu)? Feel free to show a screenshot of it: https://ww.wp.xz.cn/support/forum-user-guide/block-editor/#adding-screenshots