1998 Volkswagen Cabrio Problems with battery and starting

Hi, My car was driving fine one day and the next morning I woke up and the battery was dead. So I had it jumped and went on. When I got to my location it wouldnt start again. I figured I just needed a new battery. When I was getting a jump again to get back home before we hooked up the jumper cables, I noticed the interior light was very dim and then while wiggling the key the light came on strong and I experimented with the windows, within 5 minutes they would not go up at all then would speed up as normal, when they seemed to work normal I noticed the dash lights were on strong too but trying to start the car was still unsuccessful. After jumping, it ran fine and I got home. But again wont start. The battery cables are connected to the terminal securely with no corrosion. It seems electrical being since the power is coming and going, but when it comes the car still wont start. Could this mean the battery cables are bad due to a bad wire? What are your ideas? Thank you