Question

the bold word is a \front swabi\ (subordinating conjunction). does the highlighted comma belong?
because bruno mars had some free time on saturday, he decided to teach himself how to juggle.
keep the comma
remove the comma

Explanation:

When a subordinating conjunction (like "Because" here, a front SWABI) introduces a dependent clause at the start of a sentence, a comma is used to separate the dependent clause from the independent clause that follows. The dependent clause is "Because Bruno Mars had some free time on Saturday" and the independent clause is "he decided to teach himself how to juggle". So the comma belongs.

Answer:

Keep the Comma