Updating 5S to 8.3 storage??

After updating my 32gb 5S to 8.3, suddenly I get notifications about running out of storage! But it is not accurate, because I have only used up about 9GB, and I should have opportunity to use almost 20GB more. What's even more weird, it doesn't help deleting stuff! I have removed 2 GB of spotify music, 300pictures and about 10 apps! What is wrong? The device is also freezing alot(then quick restart to lock screen), which had never happened before.