On the right, with uneven lines you have the OffCanvas module, to which you have assigned the Menu module therefore you see the site menu there. This module can be seen even in Desktop view & Mobile view and you can also assign any other module here.
On the left, with even lines you have the Mobile Menu, which can only be seen in Mobile/Tab view. This menu is assigned to the left for devices because if you wish to hide the offcanvas then there has to be some way for the users to navigate through your site via different menu items therefore we have the mobile menu.
Right now we don't have any specific option to disable it, you need to do that on your own through the codes.
Let us know if you still have anymore doubts.
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