Upgrade from ubuntu 17.04 to some new supported version

Question

As you can tell, I'm a bit of a Linux noob. I haven't upgraded my ubuntu 17.04 and this is causing me a painful headache. I can't use apt-get at all. I imagine the reason behind this is the lack of support of my version. I tried following some tutorials, including this one: https://help.ubuntu.com/community/EOLUpgrades No matter what I do or whether I update sources.list or not, apt-get seems to still be unsupported.

If I run apt-get update, for instance, I get the following response:

Reading package lists... Done
W: The repository 'http://ppa.launchpad.net/ehbello/fritzing/ubuntu zesty Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://ppa.launchpad.net/js-reynaud/kicad-5/ubuntu zesty Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/ehbello/fritzing/ubuntu/dists/zesty/main/binary-i386/Packages  404  Not Found
E: Failed to fetch http://ppa.launchpad.net/js-reynaud/kicad-5/ubuntu/dists/zesty/main/binary-i386/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.

Or else, running apt-get upgrade gives me:

Reading state information... Done
You might want to run 'apt --fix-broken install' to correct these.
The following packages have unmet dependencies: mono-devel : Depends: mono-roslyn (= 5.10.1.20-0xamarin1+debian7b1) but it is not installed
E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).

The result of apt --fix-broken install is:

enter code here
After this operation, 13,6 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
dpkg: warning: files list file for package 'mono-devel' missing; assuming package has no files currently installed
dpkg: warning: files list file for package 'monodoc-base' missing; assuming package has no files currently installed
dpkg: warning: files list file for package 'monodoc-manual' missing; assuming package has no files currently installed
(Reading database ... 266394 files and directories currently installed.)
Preparing to unpack .../mono-roslyn_5.10.1.20-0xamarin1+debian7b1_all.deb ...
Unpacking mono-roslyn (5.10.1.20-0xamarin1+debian7b1) ...
dpkg: error processing archive /var/cache/apt/archives/mono-roslyn_5.10.1.20-0xamarin1+debian7b1_all.deb (--unpack):
 trying to overwrite '/usr/bin/csc', which is also in package chicken-bin 4.11.0-1
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Errors were encountered while processing:
 /var/cache/apt/archives/mono-roslyn_5.10.1.20-0xamarin1+debian7b1_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

The link above uses aptitude to install the packages needed, but I can't find a way to install it without apt-get.

Thanks in advance.

UPDATE That's how my sources.list file looks like:

deb http://old-releases.ubuntu.com/ubuntu/ zesty main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ zesty-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ zesty-security main restricted universe multiverse