I have a main menu on the top would it be possible to create a submenu in some pages?
yes :-D
By using sm2 in your template
Please search the forum before posting your question.
A simple search for submenu gave this as first result:
https://forum.WebsiteBaker.org/index.php/topic,11257.0.html
Lots of topics could be found on how to test if a submenu needs to be displayed.
Ruud