Use the adverb largely to mean "mostly." You might say that you're largely pleased with the way your favorite baseball team played this season if they won more games than they lost.
If a group art project was largely completed at your house, that means you primarily worked on it there, and when a once-popular novelist is largely forgotten, she's generally fallen out of favor with today's readers. Largely is a useful alternative to "mostly," "mainly," or "chiefly," and it comes from the adjective large, in Old French "broad, wide, or generous," from a Latin root, largus, "abundant, plentiful, bountiful, or liberal."