You can use SFTP in you browser to upload files to your instances.
1 - If you have not yet applied a public key to your GCP Console project or instance, obtain an SSH key pair and apply the public SSH key file to your project or instance.
2 - Open a terminal and add an entry in your ~/.ssh/config file that points to your private key. For this example, the private key file is ~/.ssh/my-ssh-key.
3 - Open your file browser and establish a connection to your instance. Paste the combined username and IP address into your file browser:
sftp://[USERNAME]@[IP_ADDRESS]/home/[USERNAME]
Reference: https://cloud.google.com/compute/docs/instances/transfer-files#filebrowser
gcloud deploydoes, this is why is "slow" - GalloCedrone