Greetings, bettina77!
It appears that some of your keyboard settings on your iPhone 6 are still working even though they're turned off since upgrading to iOS 10. That would drive me to distraction as well so I'll be glad to help you with this.
How to back up your iPhone, iPad, and iPod touch -- Whenever starting any troubleshooting, I always recommend backing up. It's always better to "have" a backup than "need" one.
1. Get help with the keyboard on your iPhone, iPad, or iPod touch -- Go to Settings > General > Keyboard and turn one of those features on, count to five, then turn off and test.
2. Restart your iPhone, iPad, or iPod touch -- Never underestimate the power of a good restart!
3. Reset iPhone settings -- Go to Settings > General > Reset > Reset All Settings. This places all of the settings on your iPhone back to factory default. Check your keyboard settings after your iPhone restarts and test again.
If you haven't backed up your iPhone at this point, I highly advise doing so now as the next steps will erase your iPhone entirely.
4. Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings -- You'll need to use iTunes on a computer to completely erase your iPhone so that you can install a fresh copy.
First time through, select "Set up as a new iPhone". You can skip logging into iTunes & App Store and iCloud for now if you wish. Check your keyboard settings and test. If the issue is resolved, continue to the next step.
5. Restore your iPhone, iPad, or iPod touch from a backup -- Follow the steps here to restore your personal information to your iPhone.
Cheers!