What is too much screen time?

I did not know the answer to your question so I research and this what I got.
The recommended screen time for children in the UK varies by age, with the World Health Organization (WHO) and NHS recommending the following limits: 

• Babies and toddlers (0–2 years): No screen time, except for video chatting with family or friends
• Preschool children (2–4 years): Up to one hour per day
• School children (5–12 years): Up to two hours per day
• Teenagers (13+ years): No more than two hours per day

Screen time can impact a child’s development, including their diet, myopia, dry eye syndrome, and posture. To help manage screen time, you can: 

• Establish age-appropriate boundaries with your child

• Negotiate the boundaries with your child

• Make sure screens are at the correct distance for your child

• Encourage physical activity in addition to screen time

• Reflect on your own level of screen time

  For adults.
  Experts recommend that adults limit screen time outside of work to less than two hours per day. This can help you maintain a healthy balance and avoid eye strain, sleep problems, and other health issues. 

  Tips to reduce screen time:

  • • Set limits: Set time limits for all devices, including your phone, tablet, and TV. 
    • Avoid screen time before bed: Try to stop using screens at least an hour before bedtime. 
    • Create a bedtime routine: Turn off notifications and put your phone in another room. 
    • Take breaks: Take regular breaks and stretch. 
  • Practice good posture: Pay attention to your posture and stand up instead of sitting too much. 
  • Avoid eating in front of a screen: Eating while watching TV or using your phone can lead to overeating. 
  • Plan your screen time: Try not to reach for your phone without thinking.