Firstly, sorry for the bad thinko at a crucial occurrence in my first comment; I was talking about half marathons all along. I'm still a novice runner; only one year in. :-). For both the half marathons, I implemented the below bog-standard rough plan (no fancy high-interval training or anything like that—it helps, though!):

- "Rest" on Mondays - walk 6K or bike 10K

- 7K run on Tuesdays

- "Rest" on Wednesdays - 10K biking

- 7K run on Thursdays

- Rest on Friday; just daily life walking/bicycling

- 5K run on Saturdays

- 10K run on Sundays[1]

Most importantly, pay attention to diet (a whole another beast). As the saying goes, "you can't out-run a bad diet!"

And here's[2] my silly 'retro' of my most recent half marathon.

[1] When training for a race, I gradually increase the Sunday distance to 13K, 15K, and 18K; reserve the best for the race day. "Taper off" the intensity of running in the last week before the race. (Specific to my situation, in retrospect, all the city bicycling I was doing as part of daily life here must've contributed to my running too. So take that "hidden training" into account too.)

[2] https://kashyapc.fedorapeople.org/half-m-Bruges-retro.html