uh, little more information needed. what grade are you in, which Spanish it is, what you think the problem is...etc.
but obviously, if you work hard enough your grade will go up. just by doing all of your homework you might be able to pull out a C or something. if you're failing you must not be doing the things you need to do to meet the bare minimum.
if you want to be cynical, if you already have an F...it doesn't get much worse than that.