Learner's definition of IMPROVE
to make (something) better
to become better
Maybe we'll buy a house when our financial situation improves.
Her writing has improved since the beginning of the school year.
The company has been having steadily improving sales.
improve on/upon (something)
to do better than (something previously done)
After months of study, I improved on my original score.
It'll be hard to improve upon the success they had last year.
[more improved; most improved]