congrats on your first job.
it's hard. food service is a difficult place to work. it's quick and hard and there isn't much room for you to slow down or take a break.
as for the first comment..while not right, let's face it other kids are not known for being politically correct. where you acting differently? giving them something to comment about?

most early entry jobs unfortunately don't provide a ton of instruction...they are fairly easy...assemble food, stock the bag, hand it off etc. and do it quickly, pleasantly. remember it is a workplace. their concern is keeping the customer happy and production moving. if there are problems, the supervisor should address them, and explain them so they can be rectified.

it sounds like maybe food service is not the right employment position for you...however realize that any form of employment will be stressful. each job has an expectation of employee performance. if you do have restrictions that impact your ability to perform, you might consider sharing them with your hiring official...ask your parents what they think.

good luck , keep trying and be patient....