floating virtual home button- how to remove?

To disable AssistiveTouch (virtual home button), go to Settings -> Accessibility -> Touch -> AssistiveTouch and turn off AssistiveTouch.

Restarting your iPhone will fix the issues.

How to restart your iPhone X, 11, 12, 13 or later

1. Press and hold either volume button and the side button until the power-off slider appears.
2. 
3. 
   
4. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force-restart your device.
5. To turn your device back on, press and hold the side button (on the right-hand side of your iPhone) until you see the Apple logo.

How to restart your iPhone 6, 7, 8 or SE (2nd or 3rd generation)

1. Press and hold the side button until the power-off slider appears.
2. 
3. 
   
4. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force-restart your device.
5. To turn your device back on, press and hold the side button until you see the Apple logo.

How to restart your iPhone SE (1st generation), 5 or earlier

1. Press and hold the top button until the power-off slider appears.
2. 
3. 
   
4. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force-restart your device.
5. To turn your device back on, press and hold the top button until you see the Apple logo.

Can't restart?

Find out what to do if your iPhone is frozen, won't turn on or isn't responding.

Make sure that you also turn off the Accessibility Shortcut.

Settings>Accessibility>Accessibility Shortcut>Off.