Menu alignment on different screen sizes

Hello
I am not sure if this is a Maxi Menu or Maxi Menu mobile question sorry so am putting it here. We use both for our website.
Could you please help me workout how I make a menu keep its centre alignment when viewing our website on a phone or smallest screen width.
I have attached 3 images to show what I mean using the same menu we have created with images.
On a desktop size setting the menu aligns centre with the images which is perfect - see attached image - maxi_menu_desktop.gif
On a tablet or ipad size setting the menu remains centred which is perfect - see attached image - maxi_menu_tablet_ipad.gif
but when viewing the same page and menu on a phone (or sizing a desktop page down in width) the menu images become left aligned - see attached image - maxi_menu_phone.gif

Would be great to know why and how to stop this happening for this menu and any we create in the future please.

Thank you

Hi
Please give me the url of the page so that I can check
CEd

Thank you
It is a page behind our member login area.
Can I send you a username and password to an email for you try?

you can use the contact form to send me the info
www.joomlack.fr/en/contact

I have received your email, please try to add this custom css in the page