Phone Storage Questions

[Zendaur]

So when I click on Storage in my Android options, my phone displays what I attached.
As you can see it is irrational and inaccurate, as when I plug my phone into my computer it says I have around 40MB (even less at times) and the visualisation doesn't match up with the numbers. Sometimes it even says I have 320-500 GB of cache in my Instagram or Google Drive (lolwut?)

My phone : Alcatel OneTouch Pop C7 7041d running Android 4.2.2

What can I do to free up space on my phone? I know 2GB isn't much, but seriously, I have no idea how to get rid of this seemingly invisible data that is taking up all my storage. I have an 8GB SD card, but I can't even download updates because my phone has 'Insufficient storage on device.' My device is rooted.

I'm sorry if this isn't the right section for this type of question, but it gets frequent posts and I think people on here would have some experience in fixing these kinds of problems.

 

[Alabalcho]

Why If your device is rooted, you have full control over it. Applications like Titanium Backup will let you see every intricate detail of where the space goes.

As for the update - backup your stuff, reset, upgrade. It's up to you to decide why you need rooted phone (and that could be the reason for wasted space).

 

[shahbaz200]

System also takes up storage from that 2GB that isn't listed in your screenshot.