Benfica will pay around €15m for Waldschmidt, who has agreed a five-year deal with the Lisbon club.
Rui Costa, Benfica’s sporting director, was in Freiburg on Tuesday to make everything clear with Freiburg.
All that is missing are some details for a player Benfica head coach Jorge Jesus is a huge fan of.
Waldschmidt impressed enough in the 2019-20 season for Germany to hand him his first three caps at senior level.
He scored eight goals in 24 appearances (15 starts) for SCF this season and was the top scorer at the 2019 Euro U-19 Championship.
Koch, 24, had been a main target for Benfica but they have turned to the experienced Vertonghen.