How do I deal with being a slower student/learner when I’m partnered with someone?

I am pretty good at working by myself and completing the work. But, when I have to work with other students I am always the slowest one in the group. It takes me a while to understand things because I have brain fog/ tension headaches. I hate being the student that is useless in a team. I asked the teacher if I could work by myself or work with a tutor but the teacher told me I have to work with other classmates because it’s apart of my grade.

I have more team work classes in the future and I wasn’t to be assets and not a liability.