The 19-year old striker had an impressive rookie season with the Union, finishing with seven goals from 17 starts, but knows he has to get better to be a consistent performer at the top level.
"I'll definitely be training and getting ready for next year," Mwanga told The Oregonian. "There are a lot of things I need to work on.
"It (MLS) was very different compared to when I played in college. I just had to make some adjustments. I was very patient and I kept working hard and waited for my time to come."
As for his future, Mwanga said that he is content to keep getting better with the Union before potentially looking abroad.
"Right now, I'm very excited about being in Philadelphia and I'm very happy playing with my team and the coaching staff," Mwanga added. "I'm just trying to focus on my time here and after my time here, we'll see what happens after that."