I have a C- in my language class, so I’m going to retake the class at a community college this summer. Will the grade I get replace the first grade? If retake more classes this way, would that change my GPA for that year?
It's unlikely that retaking the language class will REPLACE your previous grade in the class; however, it's possible that the grade you receive in your community college class will be factored into your GPA (in addition to your original C-). Because the policy varies from high school to high school, it would be best to check with your guidance counselor to see if community college classes are factored into your high school GPA.
For more information on taking community college classes in high school (including how to show colleges you took community college classes if they're not included in your GPA), be sure to read this article.