Hi, How could I add pages? if i add a bar it adds one in the same page because there is still room, but i would like a new page with new key and signatures at the top, but not a new file

You actually have to add measures that have notes in them, and you'll get a new page if it deserves one, and if you disagree with its decision to the negative, use the "new page" break from the "Breaks and Spacers" palette on the last measure on the page that you want to stay there now.