How to run a faster 5k

Trying to improve

Hello everyone. I am 21 years old, been running mostly for fun for years but recently tried to up my game a bit. I'm really loving Parkruns, I've started doing one every week and have managed to slowly knock one minute off my PB throughout 2019 from 17:51 down to my new best last week of 16:50. Now I've decided I'd like to target a sub-16 5k and would like advice from more experienced runners. I do not currently own any form of GPS watch or device (I used to but it was stolen) so my runs are simply done on time. I actually sort of prefer not having one though as it reduces the temptation to go faster on easy days. Here is my currently weekly routine:

Monday - Short 30 minute weights session followed by 1 hour easy run either on treadmill or road

Tuesday - Hard interval session. I like to change it up every week, examples include 16X20 second Hill sprints with 2:30 minute recovery and 8X3 minute reps with 90s recovery.

Wednesday - Short 30 minute weights session followed by 1 hour easy run either on treadmill or road

Thursday - 30 minute Circuit training (35 seconds on, 25 seconds off) exercises ranging from Burpees to Crunches to Lunges etc. This is a very intense workout.

Friday - Complete rest (Though I sometimes go out for a Bike ride)

Saturday - 5k Parkrun at maximum effort, usually followed by a 30 minute weights session later in the day

Sunday - 75 minute easy road run (Probably between 7-8 minute miles, not sure though as have no way to measure distance or pace)

I enjoy them but I think 3 times per week lifting weights might too often?

I'm aware doing a Parkrun every single week may be a hindrance to my training but I really enjoy them and look forward to them every week so I'd prefer to keep them that way. May also be worth noting I work nights and sometimes will do the run straight after a 12-hour shift (I actually set a few PBs straight after shifts)

May also be worth noting that my easy runs are VERY casual. I listen to music, sometimes I stop to admire a view or chat with people, the pace is generally one I could have a full conversation at with ease.

Are there changes I should make? Any advice as to what I should add/remove/adjust would be highly appreciated. Thanks!

onyourmarks41

I'd be happy with a sub 20. But i am twice your age.