The German arrived from RB Leipzig in the summer for a £47.5 million fee.
The 24-year-old has started the season impressively, playing as a striker and off the left wing.
"These were the clubs in my youth that won a lot so maybe [Cristiano] Ronaldo or when you are here, you hear [about Didier] Drogba and also Frank Lampard the manager, they have a lot of legends in the club here.
"When you come here and see they are working for the club, you see them and you were like a child like 10 or something, you see Ashley Cole, Lampard or Petr Cech you think 'it's crazy, I'm here now with them!' It's a lot of fun."