You can fix the too thick thing yeah. I had to do the same thing so hopefully this will help sorry if it doesn't. Just take the top part of your bangs and bring the part of them you don't want back so your bangs will be thinner. Using a head band to keep the extra hair back works. Then all you do is grow your bangs out again, with the bad part of the bangs grown out to the length of the hair that isn't your bangs. This usually takes awhile though so I'd grow out the extra part you don't want first. I also suggest that you get a different hairstylist and get a picture of what you want so this time the girl wont mess up. There's also pills online that makes your hair grow faster if you absolutely can't wait.