You can use one or the other, but not have both active at the same time. To disable AssistiveTouch please follow the path below,
iPhone > Settings > Accessibility > AssistiveTouch — disable, if it is disabled, momentarily enable and then disable again.
Scroll down to bottom of AssistiveTouch screen > Confirm with AssistiveTouch > disable
After confirming above, please do a forced restart following the instructions in the Apple Support article linked below. If you’re unfamiliar with the procedure, follow the step by step instructions in the article.
Force restart iPhone - Apple Support