not a track meet just cross country practice and how do I fix my lungs or whatever
You can't exactly just 'fix' them. Sounds like a problem with your throat more so anyway. If your lungs are actually affected I don't think you'll be able to know, but if there are any symptoms they'll probably show up half-way through your running practice. Good job.
For the throat, it sounds like irritation, which isn't surprising. The mucus I think is a response to the irritation. Drink a lot of fluids, try swallowing some honey, and be good to it. No inflammatory foods, don't drink anything that's too hot.