How to clean /dev/nvme0n1p3/?

My Ubuntu 22 is showing full disk used.See that /dev/nvme0n1p3 875G 824G 6.9G 100% /?But how do I cd into that?Due to this disk being full, my server is affected, several services have stopped due to no space left on device.

df -hFilesystem      Size  Used Avail Use% Mounted onudev             63G     0   63G   0% /devtmpfs            13G  1.4G   12G  11% /run/dev/nvme0n1p3  875G  824G  6.9G 100% /tmpfs            63G     0   63G   0% /dev/shmtmpfs           5.0M     0  5.0M   0% /run/locktmpfs            63G     0   63G   0% /sys/fs/cgroup/dev/loop0      128K  128K     0 100% /snap/bare/5/dev/loop1       74M   74M     0 100% /snap/core22/864/dev/loop2       67M   67M     0 100% /snap/cups/1024/dev/loop3       75M   75M     0 100% /snap/core22/1033/dev/loop4      159M  159M     0 100% /snap/chromium/2734/dev/loop5       67M   67M     0 100% /snap/cups/980/dev/nvme0n1p2  488M   84M  380M  19% /boot/dev/loop7      497M  497M     0 100% /snap/gnome-42-2204/141/dev/loop8       41M   41M     0 100% /snap/snapd/20671/dev/loop9       41M   41M     0 100% /snap/snapd/20290/dev/loop10      92M   92M     0 100% /snap/gtk-common-themes/1535tmpfs            13G     0   13G   0% /run/user/0/dev/loop11     160M  160M     0 100% /snap/chromium/2738

I have been banging my head against wall to find where those files are? where I can find and delete them?

Cannot find it using this command.

du -h --max-depth=1 / | sort -hdu: cannot access '/proc/2216465': No such file or directorydu: cannot access '/proc/2216468/task/2216468/fd/4': No such file or directorydu: cannot access '/proc/2216468/task/2216468/fdinfo/4': No such file or directorydu: cannot access '/proc/2216468/fd/3': No such file or directorydu: cannot access '/proc/2216468/fdinfo/3': No such file or directory0       /dev0       /proc0       /sys4.0K    /mnt4.0K    /srv8.0K    /media16K     /lost+found580K    /tmp5.8M    /etc83M     /boot914M    /root1.4G    /run1.8G    /home3.0G    /opt3.4G    /snap4.6G    /usr9.0G    /var24G     /

Not even this

sudo du -xh --max-depth=1 / | sort -h4.0K    /mnt4.0K    /srv8.0K    /media16K     /lost+found40K     /snap588K    /tmp5.8M    /etc914M    /root1.8G    /home3.0G    /opt4.6G    /usr9.0G    /var20G     /

Not even this

df -h --output=source,target | awk 'NR>1 {print $2}' | xargs -I {} du -h --max-depth=1 {} 2>/dev/null | sort -rh | head -n 1024G     /9.1G    /var4.6G    /usr3.4G    /snap3.0G    /opt1.8G    /home1.4G    /run/log1.4G    /run1.4G    /run1.3G    /snap/gnome-42-2204/141/usr

sudo ncdu -x / output

How do I find largest directories/files and free up space?

I know there is similar question asked How to locate and clean /dev/nvme0n1p2?

But even running commands from the answers, I cannot find directories/files taking up all of space.