en_tn/act/01/09.md

as they were looking up

"as the apostles were looking up at the sky"

he vanished into a cloud out of their sight

"He went up into the sky, and a cloud blocked their view of him and they could not see Him anymore."

looking intensely to heaven

"staring at the sky" or "gazing at the sky"

You men of Galilee

Specifically "you apostles." Though the angels spoke to the apostles, other verses suggest that other disciples, both men and women, were present at this event.

why do you stand looking into heaven?

This rhetorical question can be translated as a statement as in the UDB. (See: rc://en/ta/man/translate/figs-rquestion)