I can't open some documents on my MacBook Pro

The past several days I have had trouble opening up documents, powerpoints, photos, or video on my MacBook. If I double click it does nothing. If I say open with it will do nothing. I have even tried cleaning up my computer by transferring file to my external hard drive but the ones that don't open up when I try to transfer them will say Zero Bytes. I am a student and really need access to these files. Thank you