I wanna run 5km

[00Snitch]

I work with a bunch of 40+ years olds, one dude over 50, I'm 23. Alot of them are runners, they can all (including one lady mid 40s and the over 50 guy) do 5km in around 25 mins (ranges from 25-27). So today, I thought "eff this! If old dudes can do that shizzle, so can I!".

So for possibly the first time in my life I ran 5km today. It took me about 32min 44sec.

My thoughts are:
-I plan on doing a 2km/5km/2km/5km on mon/tue/wed/thu and probably not on the weekends, although i play some social sport on the weekends. (touch football, indoor soccer and cricket)
-How long should it take me to get my time down to around 25mins, considering I am:
-Male, 23, 182cm, 78kg
-My gf has an electronic scale at home that tells me I am ~23% fat and ~57% water something
- I smoke on the weekends, about a pack of 20 over the weekend
- I drink a fair bit on the weekends. mostly beer. in a standard night, i might go through ten 375ml full strength (~5%) beers.

My eventual goal is 20 minutes. Doable?

Any other advice?

I never even knew there was a 2p2 gym forum til about 10 minutes ago, awsome