One of the first things you need to learn about photography is that while your brain is very good at isolating a subject from the background, your camera is not. When you look at something and focus on it, your brain kind of discounts the information around it as less important, but to the camera it's all just light.
Try an experiment to train your eye: set something on a table in the middle of a room and look at it. Look at how the light interacts with it, where the shadows lie, etc. Really study it. You'll notice that while you're studying it, your brain is isolating it from the background, elevating its importance in the scene; the things around it, while you can see them, aren't really being processed as much. So now make the conscious effort to look at the entire scene instead of just the object you're looking at. Suddenly you'll see all kinds of clutter, and you'll probably notice that there's nothing about that object that specifically makes you want to look at it.
So when you're taking a photo, especially a portrait, you have to lead the eye where you want it to go. There are lots of ways of doing that, from lighting and composition to depth-of-field, but the point is that you have to deliberately remove or reduce the value of the elements in the photo that distract from the actual subject of the photo. In this case, the tree and the house are competing for attention even though we know that the subject is the person.
You need to learn to look "in to" the viewfinder instead of "through" the viewfinder.
Keep shooting!