Thank you for using Bitnami. If you use the Google's in-browser command line utility to access the server, you will use your Google account name's user instead of the Bitnami one. In order to configure the SSH credentials for the Bitnami one, you can follow this guide to get / configure the keys
In case you want to upload any file using a SFTP connection, you need to use the bitnami user and the key you configured / got. When accessing through SSH, if you use the in-browser utility, you can run
sudo su bitnami
to use the bitnami user. In case you use any other SSH client, please use bitnami and the SSH key you have.
If you launched the Bitnami solution, all the files are installed inside the /opt/bitnami folder, could you please check it again?
sudo ls -la /opt/bitnami/
I hope this helps