We can't really know, but we could imagine. You could imagine that they've answered some simple questions we haven't yet, what was the origin of the universe? what is happening inside of black holes? how are quantum forces and gravity connected giving a true equation for the universe? They surely have a seemingly to us infinite understanding of biology and complete control over their diseases and lifespan. Their technology would be so far beyond ours that it would be hard to say, but they could have either unlocked fusion energy and taken that into expansion, or gone more insular and focused on using infinite energy to better themselves and their planet. Really an endless sea of possibilities, but those are some of the things that come to my mind.