The 22-year-old joined Partizan from German second division side Munich 1860, where he spent his entire three-year spell at the club playing for their reserve team in the lower tiers.
“We brought him in as an investment for the future because he is a talented player with the level of raw quality required to play for Partizan,” the club’s director Mladen Krstajic said.
“It’s now up to him to work his way into the first team.”
Manga has made five international appearances but is yet to score for his country.
Partizan started their title defence with a 5-0 rout of first division newcomers Novi Pazar on Saturday and are away to Irish side Shamrock Rovers in the first leg of their Europa League playoff tie on Thursday.