mirroring part messes up the part

Hello Internet-

Hello I am extremely frustrated at Solidworks right now, I am using 2016 and every time I try to mirror my part it messes up the original part. I have tried to use the property manger tab to invert the image and all that but it produces the identical result. I dont know why I am having such a tremendously difficult time with something so simple, I am about to jsut stop using SW completely as my student "trial" or whatever the f is running out soon.

As you can see in image 3 it completely alters the original side, I dont know why or how but it jsut does.

SolidworksParts And Features