Hello Farzad_K,
Thanks for asking the Apple Support Communities for help with taking pictures.
Please start with this help article: Take great photos with iPhone - Apple Support
Next, please check your options with adjusting your settings, including exposure in this help article: Take photos with the camera on iPhone - Apple Support
"Adjust the camera’s focus and exposure
Before you take a photo, the iPhone camera automatically sets the focus and exposure, and face detection balances the exposure across many faces. If you want to manually adjust the focus and exposure, do the following:
- Tap the screen to show the automatic focus area and exposure setting.
- Tap where you want to move the focus area.
- Next to the focus area, drag up or down to adjust the exposure.
- To lock your manual focus and exposure settings for upcoming shots, touch and hold the focus area until it pulses; tap the screen to return to automatic settings."
Thanks and have a wonderful day.