How can you remove a glue stick from a glue gun?
If you haven't used all of the glue stick that you inserted into the glue gun, do not try to remove it. Removing the glue stick could damage the internal components of the gun - regardless if the adhesive is runny or hard.
Simply leave the glue stick in the glue gun until you use it again. Surplus glue stick may be trimmed off using a sharp knife.
When the glue stick is almost gone, you can insert another stick and continue to use the glue gun as normal.