My iPhone storage is showing almost full But i've manually delete all photos

See if this helps: Why does my iOS device say I have more photos than I can find?

Please try Lawrence's recommendation above, it has resolved a lot of issues. If it does not work you likely have a bloated "Other" (see this article) and then do a full Restore - you should not loose any data or apps if you restore from a backup.

http://osxdaily.com/2013/07/24/remove-other-data-storage-iphone-ipad/

Please follow the instructions in the article at the bottom. The process is rather straight forward as iTunes will guide you along the way. You will have to disable Find my iPhone/iPad first. Don't forget to set it back to On when you are through (iTunes should do this automatically but check any way and set Send Last Location to ON).

Connect your device to your computer. Then import all your photos from the device to the computer and backup all important documents as well. Then do a full backup to iTunes, just follow the instructions below. Then select Restore iPhone/iPad and iTunes will install a fresh copy of the current iOS and will erase all your data. After iTunes has installed a fresh copy of the iOS, it will ask you if you want to set your device as New or restore from Backup. Choose From Backup. Restoring will bring back all your Settings, Apps, Photos on Camera Roll, etc. You should not lose anything.

After completion check to see if works. There is a possibility that restoring from the backup may bring back some system/app corruption. If this occurs (unlikely) you would have to start over again, set it up as New and install all Apps manually (a time consuming process). You would also lose your photos and documents so it is important to back them up first as I mentioned above. I have done this myself several times and restored from backup with no difficulties - it takes 30-50 minutes.

Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support

If after following Lawrence's suggestion you still see the same then double check to delete all photos you can from the Photos App Camera Roll and Recently Deleted. Then go to iTunes and do a fresh backup. When you restore from that backup you will get back all the photos in Camera Roll but not any others you might have synced from the computer before. Hopefully this will clear any corrupted photos which may now reside in Other. Before doing the backup look on the Summary page of iTunes (with your iPhone connected and selected). It will show the size of the Other at the bottom usage bar. If it is larger than 1-2 GBs it is corrupted.