/root partition is filled up

Recently, my EndeavourOS install has been sending me a notification saying that my root filesystem was filled up, with 0 MiB remaining. What could be done to clean up the root system? Output of sudo du -h --max-depth=1:

9,8G	./usr
125M	./boot
50M	./root
0	./dev
du: cannot access './proc/3667/task/3667/fd/4': No such file or directory
du: cannot access './proc/3667/task/3667/fdinfo/4': No such file or directory
du: cannot access './proc/3667/fd/3': No such file or directory
du: cannot access './proc/3667/fdinfo/3': No such file or directory
0	./proc
16K	./lost+found
24K	./tmp
229G	./home
0	./sys
293M	./opt
27M	./etc
8,0G	./var
12G	./run
12K	./srv
4,0K	./mnt
259G	.

Output of df -h:

Filesystem      Size  Used Avail Use% Mounted on
dev             7,6G     0  7,6G   0% /dev
run             7,6G  1,7M  7,6G   1% /run
/dev/nvme0n1p2   20G   19G     0 100% /
tmpfs           7,6G   71M  7,5G   1% /dev/shm
tmpfs           7,6G  1,5M  7,6G   1% /tmp
/dev/nvme0n1p4  500M  324K  499M   1% /boot/efi
/dev/nvme0n1p3  259G  229G   17G  94% /home
tmpfs           1,6G   92K  1,6G   1% /run/user/1000
/dev/mmcblk0p1   15G   12G  3,4G  78% /run/media/dion/_________
/dev/nvme0n1p1   17G   24K   16G   1% /run/media/dion/71f8f1fe-5a7d-433f-aa03-84b679c7e2d9