Here’s how to change instance types via the command line

# Set Project
gcloud config set project your-project-id

# Change instance type to 2 CPU 20GB memory.
gcloud compute instances set-machine-type your-server-name \
--zone us-east1-a \
--machine-type n2-custom-2-20480

# Change instance type to original settings.
gcloud compute instances set-machine-type your-server-name \
--zone us-east1-a \
--machine-type n2-custom-2-15360