The talented winger spent last season on loan at Burnley before he was sold to newly crowned Bundesliga champions, Bayer Leverkusen last summer.
Tella, though not yet a regular at the BayArena, played a crucial role in the club’s Bundesliga success.
Die Werkself are also in the final of the DFB Pokal and semi-final of the UEFA Europa League.
“I couldn’t believe it, Arsenal was all I knew from the age of six when I got scouted,” he told VAVEL.
“It was tough because I didn’t know what I wanted to do. Maybe stay at Arsenal, try force their hand and make another decision, or if I was to go out on trials.
“I spoke to my family, I spoke to my agent and they said it’s best to go on trials to see what I can do and get out of my comfort zone.”
