Azure fundamentals can be studied in a relatively short amount of time, depending on the level of experience and understanding that a person has. If someone has a basic understanding of Azure concepts and is comfortable with using Microsoft Azure Portal, then the time required to study for Azure fundamentals may be a few hours.
If someone does not have a basic understanding of Azure, or is unfamiliar with the Microsoft Azure Portal, then the time required to study for Azure fundamentals may be considerably longer.
As with any new topic, it is always beneficial to study material that is designed specifically for Azure. This will help to ensure that the person understands the concepts and is able to apply them to the Microsoft Azure Platform.
A good place to start is the Azure Basics course, which is offered as a part of the Microsoft Azure Training program.
The bottom line is that it takes a bit of time to study for Azure fundamentals, but the payoff is a deeper understanding of the Microsoft Azure Platform and the ability to use it to your advantage.