Here is the article from Apple regarding Guided Access.

To Start a Guided Access session

1. Open the Gemini Mobile App
2. Triple-­click the Home button. For iPhone X, triple-click the side button. 
3. Triple-­click the Home button again For iPhone X, triple-click the side button. 
4. Enter your passcode
5. Disable desired buttons, touch areas, or set a time limit
6. Tap Resume

Guided Access Options

• Circle any part of the screen you want to disable and use the handles to adjust the area if you only want to disable specific buttons or areas
• Toggle Touch OFF to ignore all screen touches 
• Tap Options under Hardware Buttons to disable specific hardware
• Tap Options under Time Limit to enable a time limit and set its duration

Note: Please be sure that toggle Touch OFF to ignore all screen touches

To End a Guided Access session

1. Triple-click the Home button
2. Enter your passcode
3. Tap End

Please let me know if this resolves your issue, or if you require further assistance.