I'm creating an android game, I want to let user to get updates and new levels online. I have an account on google's cloud but there are many services and I am confused which one is more suitable.
For example: Bigtable, SQL, File storage or any other service.
Depending on what you wish, there are many things that you can do. I'm understanding that you would like to know more about the Storage options from how you are orienting your question.
If you want a good and simple storage backend you can use Cloud Firestore which is really good for Android. Another good option can be Cloud SQLwhere you can instantiate either a MySQL database or a PostgreSQL one.
As for the get updates and new levels online a possible way of integrating this might be either with Cloud Functions or by having your code deployed on App Engine. Cloud Firestore also facilitates these interactions as you can read in the previous documentation.
Have a look and let us know.
EDIT:
This is a good read that is resembling what you are looking for. Link