You’ve paid, and you’re getting your support. Send us access details to your wp-admin in a private message please – we will take a look. But in general, there are many HTML/CSS problems on your mobile version, not just the background picture. We will see what we can do, but in general, the support for the older versions was dropped a while ago – you really need to upgrade. See the other answer, please.
Tried to update the other site I asked about and ran into problems – once you reply and I sort out updating the theme, I will do it for this site and repost the info if the problem does not clear up with the update.