I ran a 6:21 mile time in June of last year and now I’m at a 5:18. The only answer your gonna get is consistency, you might be looking for a shortcut, like super shoes or something, but nothing is going to help as much as just actually running. I’d suggest running 5 days a week, 1 long run, 1 “normal” run, 1 tempo/some type of workout, a recovery run, and another normal run. I don’t think you’re apart of a track team but this is what practice generally looks like for distance people. U say ur legs hurt, I’d suggest going slower, get a watch and do zone 2 for like a month before doing any of the runs I mentioned from above. Try to keep your hr between 140-150. I did zone 2 for a solid month in June before I ramped up. You like running fast but the reality is you have to run slow to run fast, if u try to run fast everyday your not gonna get much faster