I have enough storage!

I have included an image that shows my problem more clearly ...I have an iPhone 7+ that I bought at the beginning of 2016. I had a problem in less than a year after buying it –the IOS 10 update problem–. I had to format my device and lose all of its data .. Now and about a month ago ..my device start announcing that the storage space of the device is low! My device has a storage space of 128GB –As the picture shows that I have used less than half the storage space of the device–.. But I can not even take a single picture!