How to make (mobile) background image fullscreen? (Dawn theme)

[Perziamalayeri]

Hello!

I'm new to shopify! I have no experience with coding. 

Could you please help me? I am using the "Dawn" theme. 

I used this to make my header transparent and it worked well!

https://jotting.com/shopify/how-to-make-dawn-theme-header-transparent

But: I would like to make the homepage image appear full screen on mobile. ( see example )

I would like to have a full screen image appear not only on desktop but also on mobile.

How do I do this?

My site URL: https://perziamalayeri.myshopify.com

Thank you!

Perzia