Sticky navigation, under link menu

Hi there,

How can I do the following:

1 I want to have sticky nav bar - fixed navbar - (let's call it NavbarMain) on top of the page, but
2 when the page is not scrolled I want to have just on top of NavbarMain a row with some links - linkRow - (maybe like a second menu) that is not sticky/fixed.

so when the page is not scrolled I have

linkRow
NavbarMain

after the page is scrolled I have:

NavbarMain

the linkRow will scroll and NavbarMain will replace it and stick to the top.

Thank you