Doing this dynamically requires a server side scripting language (like php). This is, as far as I know, not possible if you use Neocities.
The easiest workaround would be to just create a static html page and showing an mail where people can write their questions to. It is well possible that the first link you gave does practically the same (with the E-Mail being sent via the form where the question is entered, which again, requires php). The second link is also an alienated guestbook; if you can find a new provider, this is also a rather simple option.