Allan has decided to return to Bundesliga after a spell with Hertha Berlin two seasons ago. The midfielder is still waiting to qualify for a EU passport.
"I want to use the time in Frankfurt, so that we can talk about more than this one year at the end. I long for a certain stability and consistency," declared Allan.
"My girlfriend is coming here. She has German roots and is also pleased that the change worked out."
While talking about an extended stay with Eintracht, Allan says he hopes for the chance to play for Reds boss Jurgen Klopp.
He added: "Klopp is a great coach, I cannot think of a player who does not love him. I would like to be able to pay back his trust at some point."