Gotcha, so there’s a little bit of a language difference. “Top speed” typically implies the max speed you’re capable of hitting; you’re describing your best pace.
In any case, this is just going to be a case of “more running”. Two things I think would help are tempo runs and intervals.
Intervals you’re going to want to push yourself and run several “sets” with near complete recovery. You’re done when your performance drops by ~10%.
Tempo runs you’ll pick a little longer distance than your goal and run sub-max, striving to maintain the same pace for the duration.
Let’s say you want to run a mile, and you currently do it in 8 minutes.
A really, really easy schedule, starting from nothing:
Monday: 4-6 x 400m intervals at 1:30 each. When you’re no longer breaking 1:40, you’re done.
Thursday: Tempo run: 2 miles in 18 minutes. Run out 1 and back 1, keeping those two splits at the same time (9m each).
Saturday: Pace: just run a mile to 1.25 as hard as you can. Try to improve each week and work on your pacing so you improve your threshold over time.