Copied a bunch of files to my computer. Now it is slow even after deleting files

I needed a place to store my files so I could give the external hard drive back to a friend I borrowed it from. So I copied about 180GB of files to my macbook pro from the external, which made the amount of free space at 44 /464GB. My computer ran ridiculously slow afterwards so I deleted most of the files and brought it up to 151GB free but that only made it a tiny bit better. I even used the AppleJack repair utility but it didn't seem to help anything.
Also sometimes when I boot up the windows side of my mac that i installed through bootcamp, I get a black screen that says 'no bootable device' but if i restart it a couple of times it'll load windows which also runs as slow as the mac side.
My laptop can't even play songs without pausing several times. Everything i click takes about 5 sometimes 10 seconds to load when it was usually instant.
I'd appreciate any help. Thank you