To repair the bridge ground connection you'll need to remove the bridge post bushing and replace the wire. This video shows the easiest way to remove the bushing. Basically, remove the bridge post then then either use a matching bolt or bolt & stud insert to screw/push the bushing out. Take your time and do it carefully and it shouldn't damage anything. Replace the wire, bending the stripped end down in the post hole so it runs vertically to make a good connection, and then carefully push/hammer the bushing back in.