After update to IOS 13.4.1, appear a circle in the centre of the screen.

I had the same issue on my SE. turn off

the dwell control in Preferences > accessibility > Touch > assistiveTouch > Dwell control

Hello isaydullayev,

Based on your post it appears you have a grey circle appearing on the display of your iPhone with AssistiveTouch enabled. This seems to have started after updating your iOS version. Is that right? I’ll be happy to help.

Does the the issue continue outside of the Settings app?

Have you tried restarting your iPhone to see if the issue continues?

If so, do you know if the grey circle remains after disabling your accessibility features temporarily?

You can do so in Settings > Accessibility. 

Get started with accessibility features on iPhone

Keep me updated.

Warm Regards.