Internal storage issue

Hi all,

Newbie here. Hoping one of you guys can help me. My issue is best explained with this picture. The bar at the top says I have loads of storage still. And when you add up all the bits below it, I should also still have loads of storage. Yet the 'Available' figure is really low. Also I keep getting warnings about my storage. So what is using all my storage? And why isn't it telling me what it is? Thanks! James

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