Please follow the below steps:
1. Try to take more pictures to see if they can be saved.
2. Check whether the storage space that comes with the phone is sufficient. If necessary, free up space to store photos.
3. Go to Settings>Apps>See all apps>Find Camera>Storage&cache>CLEAR STORAGE and CLEAR CACHE. Then then try to take a photo.
4. If the above still does not help, please save your data and then restore the phone to factory settings or update to the latest system.