Improve, better, help, ameliorate are comparable when denoting to mend or correct in part or in some degree.
Improve, the general term, and better, more vigorous and homely, apply both to objects and to states or conditions that are not of necessity bad. With a reflexive pronoun improve implies a change for the better within oneself, better a change for the better in one’s social or financial status.
To help is to improve while still leaving something to be desired.
Ameliorate is used chiefly in reference to conditions that are hard to bear or that cause suffering and implies partial relief or changes that make them tolerable.