im not kidding when i tell you youre my idol daniel, your site got me into programming which is my favourite hobby. i even started learning spanish so one day ill be able to read your site without google translate !!
I believe you fix the issue of the links opening inside the menu box is by adding this to your mainmenu.html file: https://pastebin.com/raw/CF9RwjLK (I had to put it in a pastebin because neocities was fighting me). I tested this on windows 10 on a chromium browser and it works for me. It sets the base point for opening the pages in index.html instead of mainmenu.html so they don't load inside the menu box.
Well, I don't much like my fix, but I think it works, I replaced the embedded menu with an inline menu. Ugh! Oh well. I will try to learn how to embed so it works right.
Wow, thanks man! glad to hear that I help you get into programing! Your page is even better than mine, so keep it up!
Oh, and good luck learning spanish, i am sure you'll understand it in no time :D