Mobile Version needs correcting

Hi, I’ve just created a shapely site: http://davidbryercreative.com and it looks good on laptops. But when my testers open it in any other device they get this:

http://davidbryercreative.com/wp-content/uploads/2017/06/18738646_10213477023777078_1388436498872052978_o.jpg

the View Full Site button does lead to a better version, but I’d like this better version to be the first they see. Any ideas?

Thanks,
D