J2store3 Courses Category in setup

I am experiencing some problems too with this step;

I do not have a textbox, there's a dropdown list instead and even if I do select the category I do still can't publish my courses cuz it throw an error 500

Hi.

When are you getting Error 500? Did you check error log to look for hints on where error is coming from?
This is working fine for me and other users, so I guess there must be a problem that only happens in your configuration.

Sorry Antonio, I did move on with Hikashop instead, and it's working fine; I found out that there were a problem with another plugin so I had to try another eCommerce integration

No problem, glad to know that you got it working fine with Hikashop.