Heat oil in a pot and cook onion and potato until onion is softened. Then add garlic, cumin, some pepper and chili and roast 1-2 minutes.
Add broth, beans, tomatoes and quinoa. Boil up and let cook about 20 minutes with lid.
Then cook without lid about 10 - 15 minutes until the quinoa and sweetpotatoes are soft (if it get's too thick add more broth).
Add lime juice and season with salt, pepper, chili. You can also add a bit of balsamic vinegar.