How can I scale my workers

How can I scale my workers ?
One worker can handle how many jobs?

How can I scale my workers ?

Run more of them.

One worker can handle how many jobs?

Depends on its resources, its configuration, and the job resource requirement.

You can run experiments to see.

To understand how the worker works, here is a guided tour of the Java client source code: https://www.youtube.com/watch?v=n0cF3AVWxCk

Link was quite helpful there should be examples of some java code how should we write workers in optimized way.

You could use this spreadsheet template to precisely describe your workload and your current configuration. Based on that we could give concrete recommendations on how to improve performance for your processes.