The support information is below, but have you tried simply restarting the device?
Does the device have a good internet connection? Strong wifi and/or data signal?
Refer to this page for Apple Support features ➔ Contact - Official Apple Support
Select from the presented options until you find a solution for your issue, or see if there is a chat or phone call contact method offered lower on the page (you sometimes have to narrow down the options multiple times before this is shown). If you do not see your issue, keep experimenting with any series of selections until you reach one that offers a chat session or a telephone call and get the representative to redirect you.
This support article has various country telephone numbers for contacting Apple for support and service ➔ Contact Apple for support and service - Apple Support
By the way, you do not need the Gmail app. You can add his Gmail account (and others) to the Mail app that Apple provides. Read this support article for how to add an email account to your iPhone, iPad, or iPod touch - Add an email account to your iPhone, iPad, or iPod touch - Apple Support
