Olmo joined the Bundesliga side last month despite long-running reports linking him with a return to Barcelona - where he was once a youth player - alongside English giants Manchester United.
“Nagelsmann's call and Markus Krösche's visit to Zagreb made me opt for them,” Olmo told Bundesliga en Español, as cited by Diario Sport.
“It is the best place to be, since the Coach plays young players a lot. I am very happy to be here and gradually I am becoming more confident and growing into the team.”
The rising star received his first call-up to the senior Spain squad for the games against Malta and Romania in November, having also qualified to play for Croatia due to his spell in the nation.
Olmo had joined Dinamo as part of the swap deal which saw Alen Halilovic move to Barcelona in 2015 and had since emerged as a star.