I want to put the normal menu and I get only drop-down menu, where can I change it?
Also, every time I select an item in the menu, it appears underlined with a line crossing out the element. How can I deactivate it? Thank you very much.
it looks like you imported a Site from the Site Library which added a bunch of CSS to the Customizer > Additional CSS. You could delete all of this ( or cut and paste it to a text file for safe keeping ) and this will remove the menu underline and other styling that does not seem to be necessary.
For the navigation display, go to Customizer > Layout > Primary Navigation and in the Mobile Menu Breakpoint field delete the value.