Why I can't update any apps and it keeps on saying that I have insufficient storage but I think its not the problem because I have storage. So what should I do?
Usually you need at least 10 percent of your whole data storage to install applications.
You should delete some stuff or clean up the cache by going into Settings -> Storage -> Cache
If that does not help, clear the data of Google Play Store using Settings -> Applications (or Settings -> Storage -> Apps) and then swiping to the left until you get to
All applications and then search for Google Play Store and delete the data. Then start Play Store again and try it out if it works.