unable to free up space on samsung s3 mini
It might help to get a better look at your internal usage.

An app like Disk Map has a function to view disk usage. You may be able to use this to identify large files and delete them.

In this particular app, select 'Internal storage' and press the 'Disk map' button to see something like this:



And you can even long press items in this map to see options to delete them: