By default Raspberry Pi does not allocate enough of your SD card for it to be usable. Out of the box, if you run sudo apt upgrade, you’ll get a message saying that you don’t have enough disk space. Here’s how to free up more.
Open Terminal or SSH and execute the following command:
sudo raspi-config --expand-rootfs
sudo reboot
You might see an error message when running this, but I’ve ignore it and have had no issues.
You’ll find more details on this resize process here.
Jon