As I have already mentioned above, once the user run this misguided upgrade command in the terminal, the damage is done.
In spite of all the efforts and suggestions, clean install was the only way to bring the system back normal in each and all cases we saw in this forum.
Will I have to reinstall the system? for me this is no problem, after all the computer is quite full even though there is a lot of space, but how am I going to do this? is there any way to save my files? and another thing, I have zorin 15.3 core installed on c disk in dualboot with windows, and how would I reinstall the system in dualboot?
You need to backup your entire Home directory.
You can use a large capacity USB or an external SSD/HDD for that purpose.
I think the best course of action is to delete this Zorin 15,3 partition using Gparted in Live session then initiate the installer.
Since I am not an expert on dual boot, I will ask other volunteers to give you more advice.
@Kedric @Aravisian @337harvey
I am not sure if your attempt to direct update has harmed your personal files in /home partition. If not then you can use the "Something Else" method to re-install Z15.3 Core, or if you wish Z16 Core if you have a bootable USB containing that.
I always use Wolfman's (old but good) guide to using the "Something Else" method to install ZorinOS. Here is link to it on the old Forum archive. Install Ubuntu (Zorin OS) using the "Something Else" method - Old Zorin Forum archive
sudo apt-get update && sudo apt-get upgrade
Maybe that will work. Also updating from zorin 15.x to 16 is not available.
Deleting the partition and reinstalling is one way. To ensure no bleed over from the previous installation you may want to format the partition as ntfs or fat32 and then return it to ext4 in the installer. Definitely use the something else method to direct the installer to use a specific partition for root.
All right, I understand, the right thing is to backup, delete with gparted with the pendrive and install the newest one?
i gonna try
Yup.
But you could try @Michel's suggestion before wiping it.
Provided you make a good backup of your data, you have nothing to lose at this stage.
Thank you, i gonna backuping (starting backup im brazilian sorry)
Good luck 
And do comeback here if you ever need any help.
We are more than happy to assist you 
Look at the labelling.
The first 2 partitions and the last partition are labelled "ntfs" which is a file system for Windows.
Zorin 15 resides on dev/sda3.
I think you have to delete that partition and create a new partition.
I recommend not to use extended partition but use primary partition to make the future maintenance simpler.
Well I think zorin is on the 150gb disk, no? because my computer says it has 50 gigs of free space, see the next image
You mean 150GB partition.
Just be careful for those terms - they mean very different things.
Exactly. I can't speak English well, I'm 11 years old I started learning this month
I didn't know how to speak that term in English but thank you. that's right
You are only 11 years old and already started to use Linux!
Wow!
Don't worry.
I am also not a native speaker.
Back to your question, yes, it is this 150BG partition you have to delete and format to ext4 (Linux file system).
I am a native speaker and I can't speak English.
Ah, but you know how to prepare this disk for the clean install of Zorin 16.
