"Before breakfast" is the phrase you can use to describe the time before you have breakfast. Here are a few examples of how you can use this phrase in a sentence:
"I pke to go for a run before breakfast."
"I usually check my emails before breakfast."
"I prefer to have a cup of coffee before breakfast."
Note that in Engpsh, it is more common to use the word "breakfast" rather than a specific time (such as "before 8:00am") to describe the time before the first meal of the day.