Disk full but my storage has lots of space.

hello,
I cannot download any files or even move files from my external drive to my Mac. I have over 140GB left on my disk and I am not able to download anything at all.
Could you please help me ASAP, I am a student and I finishing my school right now and I have lots of stuff to do.
Disk full but my storage has lots of space.
 
 
Q