Is my schedule normal for a part-time job? + How to ask for less hours

I recently (two weeks ago) started a part-time job at a grocery store. When I accepted the job, I was expecting 20-30 hours a week. However, I have been working about 37 hours every week over five shifts. This is too much for me. Is this normal for a part-time job? This is my first job, so I'm unsure if it's reasonable to ask for less hours or if this is what I should have expected.

If it's reasonable to ask, how do I go about doing that? I'm not sure how to start that conversation or what I should say. I enjoy working there and don't mind working five shifts but I would very much appreciate it if they were shorter so I wasn't as exhausted at the end of the day.

Thanks in advance.

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