The screen timeout controls the time until the Samsung device's display goes into sleep mode. By default, the display turns off after 30 seconds of inactivity. The sleep timeout can be changed to the following options

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Display
Step 3:  Tap on  Screen timeout
Step 4:  Choose desired  Timeout
  1. Open the Settings
  2. Tap on Display
  3. Tap on Screen timeout
  4. Choose desired Timeout

Samsung Instructions