My iPhone 7 plus Camera won't focus

Taking pictures is a pretty big hobby of mine and for the past few weeks my iPhone 7 plus rear camera hasn't been working. The only time the camera is completely clear is if it is on portrait mode. When the camera is on "Photo" the camera is extremely blurry when I am trying to take a picture from a few feet back but when I am up close or right in front of something it is clear. How do I fix this? and if I can't and have to take it to a store how much would it cost?