Thank you for writing in, after some time of checking I see that you used
margin to position things out. Please remove the margins you applied on the logo, flag images, and mobile menu. Then place the logo on a separate Container, set that container's Horizontal Align to Start this will force the logo on the left-side, set the Self Flex of that container to Standard.
Set the second container's (containing flags and menu) Horizontal Align to End this will force the flags and menu on the right-side, set the Self Flex of this column to Fill Space.
Again, please remove all those margins on the elements.
This tutorial might be a bit outdated now, but this will help you understand how Flexbox works.
Hope it helps,