Unmet dependencies - How can I fix this?

Hello.
Please head over to the Software Boutique and run the "Fixes" (Last icon on the right)

Thank you for your replies. I tried Resolve Broken Packages following your instructions, but I got Package Operation Failed, with the following details:

installArchives() failed: (Reading database ... 
(Reading database ... 5%%
(Reading database ... 10%%
(Reading database ... 15%%
(Reading database ... 20%%
(Reading database ... 25%%
(Reading database ... 30%%
(Reading database ... 35%%
(Reading database ... 40%%
(Reading database ... 45%%
(Reading database ... 50%%
(Reading database ... 55%%
(Reading database ... 60%%
(Reading database ... 65%%
(Reading database ... 70%%
(Reading database ... 75%%
(Reading database ... 80%%
(Reading database ... 85%%
(Reading database ... 90%%
(Reading database ... 95%%
(Reading database ... 100%%
    (Reading database ... 652374 files and directories currently installed.)
    Preparing to unpack .../linux-image-4.4.0-92-generic_4.4.0-92.115_amd64.deb ...
    Examining /etc/kernel/preinst.d/
    run-parts: executing /etc/kernel/preinst.d/intel-microcode 4.4.0-92-generic /boot/vmlinuz-4.4.0-92-generic
    Done.
    Unpacking linux-image-4.4.0-92-generic (4.4.0-92.115) ...
    dpkg: error processing archive /var/cache/apt/archives/linux-image-4.4.0-92-generic_4.4.0-92.115_amd64.deb (--unpack):
     cannot copy extracted data for './boot/vmlinuz-4.4.0-92-generic' to '/boot/vmlinuz-4.4.0-92-generic.dpkg-new': failed to write (No space left on device)
    No apport report written because the error message indicates a disk full error
    dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
    Examining /etc/kernel/postrm.d .
    run-parts: executing /etc/kernel/postrm.d/initramfs-tools 4.4.0-92-generic /boot/vmlinuz-4.4.0-92-generic
    run-parts: executing /etc/kernel/postrm.d/zz-update-grub 4.4.0-92-generic /boot/vmlinuz-4.4.0-92-generic
    Errors were encountered while processing:
     /var/cache/apt/archives/linux-image-4.4.0-92-generic_4.4.0-92.115_amd64.deb
    Setting up linux-image-extra-4.4.0-91-generic (4.4.0-91.114) ...
    run-parts: executing /etc/kernel/postinst.d/apt-auto-removal 4.4.0-91-generic /boot/vmlinuz-4.4.0-91-generic
    run-parts: executing /etc/kernel/postinst.d/dkms 4.4.0-91-generic /boot/vmlinuz-4.4.0-91-generic
    run-parts: executing /etc/kernel/postinst.d/initramfs-tools 4.4.0-91-generic /boot/vmlinuz-4.4.0-91-generic
    update-initramfs: Generating /boot/initrd.img-4.4.0-91-generic

    gzip: stdout: No space left on device
    cpio: write error: Broken pipe
    find: standard output: Broken pipe
    find: write error
    E: mkinitramfs failure find 1 cpio 1 gzip 1
    update-initramfs: failed for /boot/initrd.img-4.4.0-91-generic with 1.
    run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1
    dpkg: error processing package linux-image-extra-4.4.0-91-generic (--configure):
     subprocess installed post-installation script returned error exit status 1
    dpkg: dependency problems prevent configuration of linux-image-extra-4.4.0-92-generic:
     linux-image-extra-4.4.0-92-generic depends on linux-image-4.4.0-92-generic; however:
      Package linux-image-4.4.0-92-generic is not installed.

    dpkg: error processing package linux-image-extra-4.4.0-92-generic (--configure):
     dependency problems - leaving unconfigured
    dpkg: dependency problems prevent configuration of linux-image-generic:
     linux-image-generic depends on linux-image-4.4.0-92-generic; however:
      Package linux-image-4.4.0-92-generic is not installed.
     linux-image-generic depends on linux-image-extra-4.4.0-92-generic; however:
      Package linux-image-extra-4.4.0-92-generic is not configured yet.

    dpkg: error processing package linux-image-generic (--configure):
     dependency problems - leaving unconfigured
    dpkg: dependency problems prevent configuration of linux-generic:
     linux-generic depends on linux-image-generic (= 4.4.0.92.97); however:
      Package linux-image-generic is not configured yet.

    dpkg: error processing package linux-generic (--configure):
     dependency problems - leaving unconfigured

I see “No space left on device” : you may have a disk full and need to cleanup some big files (photos, movies…) before retrying…

Looking for assistance with same/similar issue even though it's old, it's relevant to me.
Had loaded Signal desktop over a year ago, all working fine. Received upgrade notice and copied and pasted in the commands in Terminal but something happened that as a newbie, I am unsure if it's my fault or ???
Screenshot of my error message shows that the list of sources cannot be read. I tried to follow your advice however Software Boutique won't open either.

HELP!!!!
unmet%20dependency|352x499