You need a bigger SD card or need to clean off a lot of what you have on your existing one.
Start by shutting down the Pi, remove the SD card and make a backup of it on a different computer. There are lots of websites telling you how to copy your SD card to a new one.
If you can make a network connection to the Pi, I would copy the /home/pi/.node-red folder to an external device. that way you will
You have 12GB of room on the partition, which means you have used a vast amount up somehow. Start by doing sudo apt autoremove sudo apt clean
which might give you some space to get started.
Then try sudo ncdu /
which, if it is already installed, will take quite a time scanning the card and then will tell you where all the space is. If it says ncdu is not installed, then if the commands above released a couple of hundred k then you should be able to install it and then run it sudo apt install ncdu
Once you know where all the space is used up you can delete it.
Make sure you have anything important backed up first though.