extreme slow working after update

Hi,
I have just updated my rp3 running dietpi using the method offered by dietpi: dietpi-update.
Then i have noticed the nextcloud became slow. I have run the ncc scan which reported the lower version of ncc then the one shown in ncc
21.0.4 shown in ncc vs 20.0.9 by the scan.
After searching i wanted to check my debian version but i am not sure how to do that.
So my question is how to check debian, dietpi and ncc version and if necessary how to update them manually
thanks

First try to perform a reboot and check your system afterwards how it is going.

DietPi can be checked using dietpi-update or by running cat /boot/dietpi/.version
Debian packages can be updated using apt update && apt upgrade
OS version can be display using cat /etc/os-release
For Nextcloud you could do following to perform a manual update if needed

ncc maintenance:mode --on
sudo -u www-data php7.3 /var/www/nextcloud/updater/updater.phar
ncc maintenance:mode --off

thank you, it works as you said. I will update debian to 11.

but still my question is:
why my system that was perfect until, became so ruggish and slow after update? how can i check possible reasons?

Can you share more details what part of Nextcloud has become slow? Is it browsing the web interface, or uploading/downloading files?

Also can you share the output of the following command:

cat /var/tmp/dietpi/logs/dietpi-update.log

So we can see which APT packages have been upgraded along with the DietPi update.