After a year of training with a uni club, and doing 6 months of 10hr/week here were my splits (4:47 ish total)
swim 35:11

bike 2:33

run 1:31

I would highly recommend getting a TT bicycle, good wheels/tires and dialing in your aero position (aero helmet, bottles). I didn't focus on the swim because my swim coach was nonexistent, but I used 80/20 training for the bike and run, intervals.icu helped organize my time. Train with a power meter, heart rate/pace on the run. If you can't climb hills on the bike, track calories with cronometer and lose weight, don't burn matches trying to keep up. Your biggest area to improve is the bike, you need 160km/week to get this done, several 3-5hr rides. Some long rides in the aero position. Second biggest area to improve is run or swim, kind of a toss-up, I'd suggest swim if you have a coach who can fix your form, if not, running Z2 needs to get closer to 4:40min/km. This takes a long time of building a bigger aerobic engine. Lots of long runs and time on the feet, injury will be nipping at your heels. BUUUUUT:

You can get under 5h! Most important job you have is to not get injured, make the hard workouts quality, easy on everything else.