iPhone 8 freeze during installation

Got new iPhone 8

Had to use Apps from Cloud with Backup for installation as no longer Apps in iTunes. Apps were installing okay and checked if they needed logins. Got to Stocard and was going to check if I needed to recopy cards but when I touched the icon - everything was frozen... couldn't open anything - after holding on/off button and home button the phone started to switch of and when black with a spinning white dial - it has now been doing this for 30 minutes with no sign of moving on.. I found a website where it said touching lower volume button and home button should turn it off instantly but nothing happens.. it just keeps twirling and no progress. The installation was progressing slowly of the many apps I have - like a couple of hundred and we only have slowish internet -

When I plug into iTunes on my iMac - the iPhone is recognised but it says it has never been backed up and it keeps showing the black screen and white dial?