I've this problem and don't know what to do , i'n trying to follow these steps so i'm asking how to turn off photo syncing and to sync my device

As the article you attached says, "Within iTunes, select the device, then select the Photos pane and turn off syncing."

In other words, once you click on the device in iTunes on your computer (with the iPhone attached), you then click "Photos" near the top and uncheck the "sync photos" box.

Then you sync your device by clicking something in the lower right (it probably says "Apply", but it might say "Sync").