Packages have unmet dependencies on 18.04 upon mongodb install

So, I tried to install mongo on my local machine, a Ubuntu 18.04.

The installation came to a halt with an error

The following packages have unmet dependencies:
mongodb-org : Depends: mongodb-org-server but it is not installed
              Depends: mongodb-org-mongos but it is not installed
              Depends: mongodb-org-tools but it is not installed

[edit] I don't have the original error from the installation. However, if any of you need anything that can help, just let me know

I tried to run 'apt --fix-broken install' and it gives me

(Reading database ... 207088 files and directories currently installed.)
Preparing to unpack .../mongodb-org-server_3.6.6_amd64.deb ...
Unpacking mongodb-org-server (3.6.6) ...
**dpkg**: error processing archive /var/cache/apt/archives/mongodb-org-server_3.6.6_amd64.deb (--unpack):
trying to overwrite '/usr/bin/mongod', which is also in package mongodb-server-core 1:3.6.3-0ubuntu1
**dpkg-deb**: error: paste subprocess was killed by signal (Broken pipe)
Preparing to unpack .../mongodb-org-mongos_3.6.6_amd64.deb ...
Unpacking mongodb-org-mongos (3.6.6) ...
**dpkg**: error processing archive /var/cache/apt/archives/mongodb-org-mongos_3.6.6_amd64.deb (--unpack):
trying to overwrite '/usr/bin/mongos', which is also in package mongodb-server-core 1:3.6.3-0ubuntu1
**dpkg-deb**: error: paste subprocess was killed by signal (Broken pipe)
Preparing to unpack .../mongodb-org-tools_3.6.6_amd64.deb ...
Unpacking mongodb-org-tools (3.6.6) ...
**dpkg**: error processing archive /var/cache/apt/archives/mongodb-org-tools_3.6.6_amd64.deb (--unpack):
trying to overwrite '/usr/bin/bsondump', which is also in package mongo-tools 3.6.3-0ubuntu1
**dpkg-deb**: error: paste subprocess was killed by signal (Broken pipe)
Errors were encountered while processing:
/var/cache/apt/archives/mongodb-org-server_3.6.6_amd64.deb
/var/cache/apt/archives/mongodb-org-mongos_3.6.6_amd64.deb
/var/cache/apt/archives/mongodb-org-tools_3.6.6_amd64.deb

Then I tried to 'apt-get install -f' and it returns the same error as it did on --fix-broken. Tried to purge mongodb, tried to delete repositories, edited source list to work with 16.04, tried apt remove, tried apt autoremove.

I'm running out of options. Can anyone help me?

[edit]

Source list goes as follows:

# deb cdrom:[Ubuntu 17.10 _Artful Aardvark_ - Release amd64 (20180105.1)]/ artful main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://br.archive.ubuntu.com/ubuntu/ bionic main restricted
# deb-src http://br.archive.ubuntu.com/ubuntu/ artful main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://br.archive.ubuntu.com/ubuntu/ bionic-updates main restricted
# deb-src http://br.archive.ubuntu.com/ubuntu/ artful-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://br.archive.ubuntu.com/ubuntu/ bionic universe
# deb-src http://br.archive.ubuntu.com/ubuntu/ artful universe
deb http://br.archive.ubuntu.com/ubuntu/ bionic-updates universe
# deb-src http://br.archive.ubuntu.com/ubuntu/ artful-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://br.archive.ubuntu.com/ubuntu/ bionic multiverse
# deb-src http://br.archive.ubuntu.com/ubuntu/ artful multiverse
deb http://br.archive.ubuntu.com/ubuntu/ bionic-updates multiverse
# deb-src http://br.archive.ubuntu.com/ubuntu/ artful-updates multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu artful partner
# deb-src http://archive.canonical.com/ubuntu artful partner

deb http://security.ubuntu.com/ubuntu bionic-security main restricted
# deb-src http://security.ubuntu.com/ubuntu artful-security main restricted
deb http://security.ubuntu.com/ubuntu bionic-security universe
# deb-src http://security.ubuntu.com/ubuntu artful-security universe
deb http://security.ubuntu.com/ubuntu bionic-security multiverse
# deb-src http://security.ubuntu.com/ubuntu artful-security multiverse
deb http://archive.ubuntu.com/ubuntu bionic universe
# deb-src http://archive.ubuntu.com/ubuntu artful universe
deb http://repository.spotify.com stable non-free
# deb-src http://repository.spotify.com stable non-free
# deb-src http://repository.spotify.com stable non-free

[edit2]

Tried sudo apt-get purge mongodb mongodb-server mongodb-server-core mongodb-clients and it returns this

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package 'mongodb' is not installed, so not removed
Package 'mongodb-clients' is not installed, so not removed
You might want to run 'apt --fix-broken install' to correct these.
The following packages have unmet dependencies:
mongodb-org : Depends: mongodb-org-server but it is not going to be installed
            Depends: mongodb-org-mongos but it is not going to be installed
            Depends: mongodb-org-tools but it is not going to be installed
E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).