[Q] How to free up space on internal memory? topic

My kid's SM-T230NU is out of space. Internal storage shows 775MB free. However, the SD Cards shows 29.34/29.71GB free. I can't seem to move anything to the SD card under the "applications" tab. It is rooted, TWRP recovery, SDFix app installed.

What am I doing wrong? How do I get stuff off the internal drive and onto the humungous SD Card that's sitting unused?

Thanks for any help!