try downloading CCleaner from the app store. You dont need to pay for the Pro version(it only gets rid of the ads in the app). Anyways, let it setup and do a scan and it may be able to find any hidden cache and file systems, duplicates, etc. and might resolve your storage issues. Hope that Helps
Also, Google Files has a Great Option for cleaning your system files, finding duplicate pictures, and has a very clean interface that breaks down what each section is using which memory/data and the steps for optimizing it.