How to Run Faster? How to Train For a Half Marathon and Marathon?

Good day.

I'm 55 and I've been running for a long time, my usual distance is 10-15 km and 21 sometimes. My average pace is 6:15 min/km. I do interval running sometimes as well.

Now, I want to run my first marathon. Is it enough to run 10-15 km every other day at a slow pace without ambition (I can talk during running) or is it advisable to move on?

Thank you.

Good afternoon,

My height is about 2 meters. I know about recommendations on power trainings for tall people. Are there recommendations for such people if we say about long-distance running (half-marathon, marathon)?

I have lots of weight. At the moment I run 5 km every two or three days, plus I train in the gym. I limit my food consumption but sometimes I can break my diet and begin to eat a lot.     

I would like to take part in a marathon.        

How many times a week do I need to run (how many times a week and how long should my running training be)?

How many kilometers, on average, per week should I run when training for a half-marathon and marathon?

What period, in your opinion, is required for physiological adaptation to low heart rate training loads (slow running for building an adequate aerobic base) and whether or not faster sessions, strength exercises, bodyweight moves or gym exercises (physical fitness/ running-specific exercises) should be included during this period? Beginners and/or runners after a break/sickness can be used as an example.

Thank you!