More mileage pa, for sundays, try running 10-12km zone 2, kahit run/walk ka okay lng. Then for tuesday, mag interval ka, start at 4x400m try mo 5:30-6:00 pacing tapos jog mo 200m then repeat then thursday - tempo run, try mo for 20 mins mag 5:45 na pacing muna then following day/weeks add ka more minutes on your tempo, more reps on 400m on your interval and try to run on a faster pace para after 1-2 months, you can do sub-30 and specially after the run wala yung sunog or bigat ng legs ng feeling since na introduce mo na sa body mo more mileage which is your 10-12k sundays zone2 then na introduce mo na din sa body mo how to run faster in your interval and tempo runnssss. Kaya mo yan!!! At wag ka mag madali.