ad 1) I don't know. I got only message if somebody respond, maybe he has mail redirect - check if all messages came from this same @.
ad 2) I don't have iPhone to check, only browser emulators. But if you don't have many submenu items, maybe you can set to display all of them by default. Read tip #4 from: https://www.joomshaper.com/documentation/helix-framework/helix-ultimate-2/customization-tips
ad 3) your website don't work right now, you have error
"Call to undefined method Joomla\Database\Mysqli\MysqliDriver::query()" - check on forum.joomla.org what it can be.