Running is all about technique. Humans are made for running. That means that our whole body is involved in the running process. There was a time, when I thought that running is only done by our legs, but that’s not true. As every movement of our body it starts at our body center. Every movement of arms and legs has an effect on our whole body and therefor finds it countermovement in the opposite part of our body. That’s why a trained core is as essential as the movement of the arms and the upright position of your head.
When all your bodyparts act together running becomes quite a relaxed activity.

Work on an upright posture. If you are standing upright your body mass should be inline. You should stand as tall as it is possible to you.
Feet, knees, hip, chest, shoulder and head all in one line. The whole body should be relaxed. This is your bodies normal posture. You should be able to stay as upright as this while running.
To run the whole body should lean forward. It’s important that your body leans forward as a whole and you DON’T bend your hip. This is one of the main mistakes, together with tilting the chin up and crunching your shoulders. If you bend your hip the power can’t flow through your body and running becomes more difficult.

My experience shows, that the posture of your upper body is the most essential. Start working on that.
Second come the stride and the stride rate. If you keep your body straight and lean slightly forward which makes the running process a constant falling, your natural reflex will let you land on your for- to mid-foot. (And not your heel) That is where you want to learn for the most healthy absorption of the the impact of landing. Once again, if you take a lot of attention of your body posture the mid-foot is where you are going to land anyway. In order to use the natural muscle-tension your stride rate should be between 180 and 200 bpm. If that’s to fast for you make smaller steps. The main difference between running fast or slow is not den stride rate but the length of your steps. The faster you run the bigger your steps become. Always staying in the range of 180-200 bpm.