I have run the cmd, but the problem still persists = missing dependencies.
This is the reply in the terminal when i tried to update-upgrade a package (( Express vpn )).

Yes i’m root.

sudo apt update && sudo apt install --only-upgrade expressvpn
[sudo] password for debian2:
Get:1 file:/usr/lib/expressvpn/repo_mirror.list Mirrorlist [117 B]
Hit:3 http://deb.debian.org/debian bullseye InRelease
Hit:4 http://security.debian.org/debian-security bullseye-security InRelease
Hit:5 http://deb.debian.org/debian bullseye-updates InRelease
Get:2 https://repo.expressvpn.com/public/deb/debian any-version InRelease [4,580 B]
Hit:6 https://deb.librewolf.net bullseye InRelease
Fetched 4,580 B in 1s (7,459 B/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
2 packages can be upgraded. Run 'apt list --upgradable' to see them.
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
You might want to run 'apt --fix-broken install' to correct these.
The following packages have unmet dependencies:
linux-image-amd64 : Depends: linux-image-5.10.0-30-amd64 (= 5.10.218-1) but it is not going to be installed
E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).
debian2@debian1:~$ apt --fix - broken install
E: Command line option --fix is not understood in combination with the other options
debian2@debian1:~$ apt --fix-broken install
E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
debian2@debian1:~$ root
bash: root: command not found
debian2@debian1:~$

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You forgot to use the sudo prefix!
"root" isn't a valid command. The command you want is

I just tried adding sudo and got the below.

debian1@debian1:~$ sudo apt --fix-broken install
[sudo] password for debian1:
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
libwpe-1.0-1 libwpebackend-fdo-1.0-1 linux-image-5.10.0-23-amd64
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
linux-image-5.10.0-30-amd64
Suggested packages:
linux-doc-5.10 debian-kernel-handbook
The following NEW packages will be installed:
linux-image-5.10.0-30-amd64
0 upgraded, 1 newly installed, 0 to remove and 2 not upgraded.
33 not fully installed or removed.
Need to get 0 B/55.7 MB of archives.
After this operation, 318 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
(Reading database ... 198609 files and directories currently installed.)
Preparing to unpack .../linux-image-5.10.0-30-amd64_5.10.218-1_amd64.deb ...
Unpacking linux-image-5.10.0-30-amd64 (5.10.218-1) ...
dpkg: error processing archive /var/cache/apt/archives/linux-image-5.10.0-30-amd
64_5.10.218-1_amd64.deb (--unpack):
cannot copy extracted data for './boot/vmlinuz-5.10.0-30-amd64' to '/boot/vmlin
uz-5.10.0-30-amd64.dpkg-new': failed to write (No space left on device)
dpkg-deb: error: paste subprocess was killed by signal (Broken pipe)
Errors were encountered while processing:
/var/cache/apt/archives/linux-image-5.10.0-30-amd64_5.10.218-1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
debian1@debian1:~$

You've run out of disk space! You'll have to clear some space before proceeding. The df command will show you which disk is full or almost full. Get rid of some stuff before trying this again. With Debian distros, a good thing to use automatically in this kind of situation is . It cleans out old downloaded packages.

I have plenty of space on my HDD, close to 2TB left.
I do get an error on start up something like no space available on boot but not sure about ((Boot)) What can be done about this ?
==========================================================================================
I ran auto clean, all went well but got the below after trying to fix broken dependencies.

debian1@debian1:~$ sudo apt --fix-broken install
[sudo] password for debian1:
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
libwpe-1.0-1 libwpebackend-fdo-1.0-1 linux-image-5.10.0-23-amd64
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
linux-image-5.10.0-30-amd64
Suggested packages:
linux-doc-5.10 debian-kernel-handbook
The following NEW packages will be installed:
linux-image-5.10.0-30-amd64
0 upgraded, 1 newly installed, 0 to remove and 2 not upgraded.
33 not fully installed or removed.
Need to get 0 B/55.7 MB of archives.
After this operation, 318 MB of additional disk space will be used.
Do you want to continue? [Y/n] Y
(Reading database ... 198609 files and directories currently installed.)
Preparing to unpack .../linux-image-5.10.0-30-amd64_5.10.218-1_amd64.deb ...
Unpacking linux-image-5.10.0-30-amd64 (5.10.218-1) ...
dpkg: error processing archive /var/cache/apt/archives/linux-image-5.10.0-30-amd64_5.10.218-1_amd64.deb (--unpack):
cannot copy extracted data for './boot/vmlinuz-5.10.0-30-amd64' to '/boot/vmlinuz-5.10.0-30-amd64.dpkg-new': failed to write (No space left on device)
dpkg-deb: error: paste subprocess was killed by signal (Broken pipe)
Errors were encountered while processing:
/var/cache/apt/archives/linux-image-5.10.0-30-amd64_5.10.218-1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
debian1@debian1:~$

did you try that autoclean command?
It is your /boot partition, which usually contains only a few files required by the boot process. It looks like this partition is full.
You may also try sudo apt autoremove

Can the boot partition be increased and how ?

yes, it can be as any other partition, if you have free space. But it is not an easy case, because an incorrect modification may make your system dead (cannot boot any more).
Did you check already this filesystem? What is inside, how "big" is it? Do you really need to do that or better to remove some old files?

I would need to resize it.
Not many files on it & plenty of HDD space.
Using LVM / Encrypted volume etc.

It was advised to remove old kernels but keep 3,
I recommend keeping the original, the latest, and the one before the latest. The lowest number is normally the shipping kernel, the highest number will be the latest.

Just to be sure, can you mark off the kernels according to the above ?

I’ll try this first before trying to resize the boot partition & after i do a complete system backup...This will take a while.

There is something else there ((Grub)) this is from the terminal,

debian1@debian1:~$ apt-get-autoremove --purge
bash: apt-get-autoremove: command not found
debian1@debian1:~$ ls /boot
config-5.10.0-20-amd64 System.map-5.10.0-20-amd64
config-5.10.0-21-amd64 System.map-5.10.0-21-amd64
config-5.10.0-22-amd64 System.map-5.10.0-22-amd64
config-5.10.0-23-amd64 System.map-5.10.0-23-amd64
config-5.10.0-24-amd64 System.map-5.10.0-24-amd64
config-5.10.0-25-amd64 System.map-5.10.0-25-amd64
config-5.10.0-26-amd64 System.map-5.10.0-26-amd64
config-5.10.0-27-amd64 System.map-5.10.0-27-amd64
config-5.10.0-28-amd64 System.map-5.10.0-28-amd64
config-5.10.0-29-amd64 System.map-5.10.0-29-amd64
grub vmlinuz-5.10.0-20-amd64
initrd.img-5.10.0-20-amd64 vmlinuz-5.10.0-21-amd64
initrd.img-5.10.0-21-amd64 vmlinuz-5.10.0-22-amd64
initrd.img-5.10.0-22-amd64 vmlinuz-5.10.0-23-amd64
initrd.img-5.10.0-23-amd64 vmlinuz-5.10.0-24-amd64
initrd.img-5.10.0-24-amd64 vmlinuz-5.10.0-25-amd64
initrd.img-5.10.0-25-amd64 vmlinuz-5.10.0-26-amd64
initrd.img-5.10.0-26-amd64 vmlinuz-5.10.0-27-amd64
initrd.img-5.10.0-27-amd64 vmlinuz-5.10.0-28-amd64
lost+found vmlinuz-5.10.0-29-amd64
debian1@debian1:~$

typo, it is not

I tried it & it won’t work.
Going to try deleting old kernels, just waiting for specific instructions as I'm only a typical user, not an advanced one...Nothing goes wrong much with Debian, so i don’t need to learn much, unlike windows.
I’m going to enlarge the partition after i make a full system backup.

it should work. I mean in general it works, and usually it won't fail. Would be nice to show us what did you really try and what's happened. I'm really sure we can help you to fix it. Enlarging that partition is much more difficult.

I did try this but don’t remember the exact results, but enough space still not available.

ypo, it is not
Code:

apt-get-autoremove --purge but apt-get autoremove --purge
^

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