New here, but how do learn if my paycheck is being taxed too much?

Please be patient and redirect me to the proper place for my question if this isn’t it. But:
I’m making 28$/hr at this new place, but my paycheck is cut short by almost 25% thanks to OASDI, Iowa state, Federal and Medicare. And this doesn’t sit right with me.
As a single guy with no kids, the only thing I can think of is during the onboarding process I marked that this was my second job back when I was working part time at a local grocery store. I’ve now dropped the grocery store job to have my weekends back, so would switching that back fix the issue?
The HR department for my job is fairly confusing to navigate in their system so I’m dreading reaching out to them