display area of a background image on a mobile

I’ve just created a wordpress website for the first time – https://roverandoutdogwalking.co.uk/ – using Tylor Moore’s video and template ( which is a great guide and I’ve not have got this far without it ! )

My only worry I have at present is when I view my site on a mobile device any background image I’ve used defaults to the left. I want to change this so I can pick the area to display. I suspect that it’s not as easy as “display this area” option (as I can’t find one !) So is it a widget or do I need some fancy coding to get round this (in which case I’ll leave it with the default at present).

Thanks for reading