I took this half-semester course that I needed to be done with by a certain date in order to apply to a program and I got a C in that class. I didn’t learn that much because, in all honesty, the teacher was not the best teacher, in fact, her class was unnecessarily difficult and she taught material that had nothing to do with the subject. That same semester at the college I work at I found out that they offered the same research course but in the other half of the semester. I was able to take the course for free, so I decided to retake the course and was able to get an A. How would this affect my GPA?
Yes, it will if your college is OK for retaking a class at C. Most of the colleges don’t let you retake a class if you already received a B or better. If that’s the case then of course you can transfer those credit to your current college and your gpa will most probably going to increase.
Please note that I am assuming that your college accepts credits from that other college.
That is not generally correct. Retaking a course at another school will not affect your GPA at your current school. Your current school may accept credit for the course, but most will not include the new grade for GPA purposes. It can help if you plan to transfer, however, since the four-year school may recalculate your GPA to include all schools attended.