Luckily they gave me another job in the restaurant.
Why did they give you another job?
They've decided that I'm better fit for that job.
It's good that your employers want to work with you and utilize your skills. Be grateful you still have a job and try to do your best at keeping it.
I'm going to quit next week.
I have to advise against that, unless you have a much better job already lined up.  Your employers seem to have been quite forgiving in granting you this second chance, and you shouldn't betray them by quitting so suddenly.  They could give you a bad reference, which would make it much harder for you to find another job.