Solder any severed connections. I recommend referencing Wie man Lötverbindungen herstellt und entlötet for how to do this!

If necessary, you may have to strip some of the casing to expose enough of the wires to be able to reconnect them. You can get away with using scissors if nothing else, but I recommend using a wire stripper for this purpose, as instructed in Kabel abisolieren.