@The Syndicate's diagnosis is right. Your whole package set is probably out of whack. I suspect you have different versions installed in this piecemeal way. Take your peddle off the gas when you are trying to figure out what's wrong.
Don't rush everything into one command. Do not try to do the automatic thing when there are malfunctions. Run "sudo apt-get update" (I'm old fashioned on the '-get' part, apt is what they suggest now, but I'm not changed over.) Review if it can talk to servers correctly. It may be looking for files on versions that you are no longer running. All of this is configured in /etc/apt/sources.d, most likely. Once you get the update to run, try next setp.
Find out how bad your update problem is going to be. Run
apt-get upgrade
DO NOT use -y, don't make this automatic. This will do nothing, it will review changes it wants to make. You need to know what things you have now are contradicting what you want to install. You may be able to run "apt-get install xyz" to get a particular package. The message about fortune is telling you that the package you are asking for does not exist by that name anymore. The error you got about other things required by fortune-mod was telling you it requires a newer or older package of something else but the automatic updating system was not pulling the version you needed. In presence of danger, try to understand what's going wrong.
The error you got happens when you surf around the net and pull in versions of packages that are not from the main repositories. You get newer versions of things that contradict what the main Ubuntu wants to do.
The request for "linux-image-4.13.0-37-generic" signals the fact that the apt upgrade will often refuse to fiddle with kernel packages. I'm using Ubuntu 18.04 after upgrading from 17.10, here are all of the linux-image files I have:
$ dpkg -l | grep linux-image
ii linux-image-4.13.0-36-generic 4.13.0-36.40 amd64 Linux kernel image for version 4.13.0 on 64 bit x86 SMP
ii linux-image-4.13.0-39-generic 4.13.0-39.44 amd64 Linux kernel image for version 4.13.0 on 64 bit x86 SMP
ii linux-image-4.15.0-20-generic 4.15.0-20.21 amd64 Signed kernel image generic
ii linux-image-extra-4.13.0-39-generic 4.13.0-39.44 amd64 Linux kernel extra modules for version 4.13.0 on 64 bit x86 SMP
ii linux-image-generic 4.15.0.20.23 amd64 Generic Linux kernel image
The kernels 4.13 are old ones still floating about. If you are on current Ubuntu, your kernel would be 4.15.0
$ uname -a
Linux delllap-16 4.15.0-20-generic #21-Ubuntu SMP Tue Apr 24 06:16:15 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
Sometimes it is easier to work this out with the package manager named synaptic. Have you tried it? Its old school, but helpful. Maybe your system is no so far gone, if you can succeed with
apt-get install synaptic
then run
sudo synaptic
it gives you a more granular view of your situation.
