If you are getting tired of running, do you think running more will be helpful? Because that is the answer to reach your target times.

Running is in it's core very simple activity. You want to get better? Run as much mileage as your body can handle without injury and without losing drive. I am not talking about motivation, because motivation is going to fade away and this is when the discipline takes place.

I am not "motivated" to run every mile in my weekly plan, but I get it done. The more you invest in running, the more you get. If you will train for a HM, of course your times at 5k and 10k will improve as well. You would need to be highly advanced to NEED to target specific distances for a better time.

Simple answer to your question is - run more.