Hi Ronnie ...
15% free disk space is cutting it close. Better to free up more disk space.
have losts of pics and some video.
That's why Apple recommends backing up your important data on a timely basis. You can recover the lost video if you have a backup to restore from.
It's possible the startup disk needs repairing.
Launch Disk Utility located in HD > Applications > Utilities
Select the startup disk on the left then select the First Aid tab.
Click: Verify Disk (not Verify Disk Permissions)
If the disk needs repairing, restart your Mac while holding down the Command + R keys. From there you can access the built in utilities in OS X Recovery to repair the startup disk.