The Toffees have reportedly rejected a £12 million bid from the German Bundesliga side for the Anglo-Nigerian who moved to the Goodison Park in January 2017.
Since his switch from Charlton Athletic, Lookman has struggled for regular playing time at the Merseyside club and spent the second part of the 2017-18 campaign on loan at the Red Bull Arena where he returned five goals in 11 games.
However, Rangnick - the club’s former sporting director - gave updates about the club’s potential signings and revealed the youngster’s desire to return to the German top-flight after his appointment as the new head coach on Monday.
"I think three more signings is realistic. We're still in talks over Ademola Lookman, we want him back and he wants to come," Rangnick told club website.
"We're also looking at something in central midfield, whether that's a no. 6, 8 or 10.
"Our goal is to develop further in every key area and make our playing style something to be feared again.
"We want to be able to get into sixth or seventh gear again so that we can't get the best possible results."
#Rangnick with a transfer update: "I think 3 more signings is realistic. We're still in talks over @Alookman_ - we want him back and he wants to come. We're also looking at something in central midfield, whether that's a no. 6, 8 or 10." #DieRotenBullen pic.twitter.com/TVK4KTCvCz— RB Leipzig English (@RBLeipzig_EN) July 9, 2018