You've gotten good advice here, but let me add that everyone is 'stupid' about something and for varying lengths of time. When I started my job it made no sense at all. Now I see that it is really straightforward. But the way I was taught wasn't the way I prefer to learn.

Your coworkers probably think they are helping you. Take a few moments to think over what you are still struggling with, and if you see some common thread, ask the coworker whose comments are most easily understood to help you.

Some things--for example, interacting with random people who come in off the street, is a longer learning curve. "I'm still new here, but I am trying!" might be your best bet if you become flustered there.

Good luck. I don't think you are stupid. Your post was well-written and your thinking was insightful and organized. Stay mindful of your strengths and weaknesses, ask for help from a good-fit coworker, and you should do fine. Courage!