Problem transferring videos to pc

[questionsiphone7+]

Hi, I am having problems transferring videos to my pc, when I transfer videos, it ends up being an audio file once its done. Its very weird since I am transferring a video to my pc then once its completed its an audio file! No video at all just the audio of the video transferred and the video part did not copy. The video is around 8 minutes long. Plus the weird thing is that every time I copy it into the pc the storage of my iphone builds up! Which is super weird! I noticed every time I try again to copy the video to my pc the iphone storage builds up. Now my storage is full because of this. Remember I am copying to the pc. And not to the iphone. But it just builds up. The video becomes an audio once done transferring to pc! And storage builds up! I have an iPhone 7 Plus. Please help! Thanks!