Inconveniently made submenu items on a smartphone

the menu on the smartphone is inconvenient.
The menu item with sub-items is not indicated in any way. no arrow to the right.
when you click on a menu item with sub-items, not only the submenu opens, but also the page to which the link leads. similarly when trying to close a submenu. the only resolve is to remove the link from the menu items with sub-items. if you click on the right, the effect is the same. no space has been allocated for the arrow to open the submenu.
if a submenu opens, it overlaps the bottom menu items. it is not comfortable. the bottom menu items do not move down.
repeated clicking on a menu item with sub-items does not close the sub-menu. to close you need to click somewhere down on a white background.