Fight takes place in the airport
Oliver swapped places with Hawkeye
Both sides have basic knowledge of each other abilities
T'Challa is bloodlusted he's after Bucky to avenge his father's death
All Oliver has to do is just buy Cap and Bucky some time untill Both of them get to the Quinjet and escape.
Oliver: "We haven't met yet.. I'm Oliver.."
T'Challa:" I don't care!!"
Then the fight begins