I’m not sure how much longer Purism is going to support Amber, but it is recommended to upgrade to Byzantium.
Make a backup of any files on your laptop that you can’t lose (on an external drive, USB Flash memory or cloud).
Then, edit your sources.list file:
sudo nano /etc/apt/sources.list
Change amber to byzantium in the file and save it (CTL+X, then Y, then ENTER).
Then issue the following commands:
sudo apt update
sudo apt full-upgrade
When done, reboot.