Some progress, at least. Not sure if this will work, but try it.
sudo pacman -R telepathy-kde
checking dependencies...
warning: dependency cycle detected:
warning: telepathy-kde-integration-module will be removed after its telepathy-kde-common-internals dependency
Packages (12) telepathy-kde-accounts-kcm-23.04.3-1
telepathy-kde-approver-23.04.3-1
telepathy-kde-auth-handler-23.04.3-1
telepathy-kde-call-ui-23.04.3-1
telepathy-kde-common-internals-23.04.3-1
telepathy-kde-contact-list-23.04.3-1
telepathy-kde-contact-runner-23.04.3-1
telepathy-kde-desktop-applets-23.04.3-1
telepathy-kde-filetransfer-handler-23.04.3-1
telepathy-kde-integration-module-23.04.3-1
telepathy-kde-send-file-23.04.3-1
telepathy-kde-text-ui-23.04.3-1
Total Removed Size: 12.87 MiB
:: Do you want to remove these packages? [Y/n] Y
:: Processing package changes...
( 1/12) removing telepathy-kde-text-ui [######################] 100%
( 2/12) removing telepathy-kde-send-file [######################] 100%
( 3/12) removing telepathy-kde-filetransfer-ha... [######################] 100%
( 4/12) removing telepathy-kde-desktop-applets [######################] 100%
( 5/12) removing telepathy-kde-contact-runner [######################] 100%
( 6/12) removing telepathy-kde-contact-list [######################] 100%
( 7/12) removing telepathy-kde-call-ui [######################] 100%
( 8/12) removing telepathy-kde-auth-handler [######################] 100%
( 9/12) removing telepathy-kde-common-internals [######################] 100%
(10/12) removing telepathy-kde-integration-module [######################] 100%
(11/12) removing telepathy-kde-approver [######################] 100%
(12/12) removing telepathy-kde-accounts-kcm [######################] 100%
:: Running post-transaction hooks...
(1/3) Arming ConditionNeedsUpdate...
(2/3) Updating icon theme caches...
(3/3) Updating the desktop file MIME type cache...
Moderator edit: In the future, please use proper formatting: [HowTo] Post command output and file content as formatted text
sudo pacman -R kholidays5 kxmlgui5 kcompletion5
KDE packages have been renamed recently, in readiness for Plasma6 in January. I can see this is particularly troublesome here.
checking dependencies...
error: failed to prepare transaction (could not satisfy dependencies)
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by blinken
:: removing kholidays5 breaks dependency 'kholidays' required by calendarsupport
:: removing kholidays5 breaks dependency 'kholidays' required by kalarm
:: removing kxmlgui5 breaks dependency 'kxmlgui5' required by kbookmarks5
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kbruch
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kcalc
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kcolorchooser
:: removing kcompletion5 breaks dependency 'kcompletion' required by kdebugsettings
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kdebugsettings
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kgeography
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kmix
:: removing kcompletion5 breaks dependency 'kcompletion' required by kmix
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kmousetool
:: removing kholidays5 breaks dependency 'kholidays' required by kopeninghours
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by krfb
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by kruler
:: removing kcompletion5 breaks dependency 'kcompletion5' required by ksysguard
:: removing kxmlgui5 breaks dependency 'kxmlgui5' required by ksysguard
:: removing kcompletion5 breaks dependency 'kcompletion5' required by ktextwidgets5
:: removing kcompletion5 breaks dependency 'kcompletion' required by libkdepim
:: removing kxmlgui5 breaks dependency 'kxmlgui' required by libkipi
:: removing kcompletion5 breaks dependency 'kcompletion' required by libkmahjongg
:: removing kholidays5 breaks dependency 'kholidays5' required by plasma-workspace
Moderator edit: In the future, please use proper formatting: [HowTo] Post command output and file content as formatted text
Let’s try this:
sudo pacman -Rs kde-applications
checking dependencies...
error: failed to prepare transaction (could not satisfy dependencies)
:: removing signon-kwallet-extension breaks dependency 'signon-kwallet-extension' required by kaccounts-integration
:: removing kio-extras breaks dependency 'kio-extras' required by plasma-workspace
Moderator edit: In the future, please use proper formatting: [HowTo] Post command output and file content as formatted text
would it be easier to reinstall KDE?
OK. Is a complete reinstall an option for you?
may be the easiest way out. What command?
It’s not that easy. You’ll need to download the latest ISO and install from scratch. Which do you want, XFCE or KDE?
quite happy with XFCE. But please tell me all I have to do, don;t want to get into a bigger mess 
Well, to start with, you’ll probably want to save your personal files to a USB drive, as reinstalling will destroy everything. You can download the ISO here. Boot with it, and follow the installation instructions of the installer. That’s really all I can offer from this point forward.
Except, download the full ISO, not the Live one.
OK thanks. I’ll try to do this when I have time. Is it not possible to keep my ‘home’?
Is it on a separate partition?
yes, it is
In fact I think it is…with all other distros I had a special partition but I didn’t install this one
Then yes, you can (if its a separate partition). When installing Manjaro, use the manual partitioning method instead; format your / partition, and any others necessary, but don’t choose to format the /home partition. Just make sure to add the appropriate mountpoints as needed for all partitions (/boot/efi, /, /home, swap).
The mistake you originally made was probably trying to install Xfce on top of KDE, I’m guessing. Now you see the result of that. 
how can I find out if I have a separate partition?
sudo blkid
Look for a partition with only `/home’.
ok thanks. wish me luck. And thank you for your help. A pity there is no easier way out