Saya berbisik kepadanya bahwa agenda hari ini sangat padat.

berbisik literally means “to whisper.” In Indonesian, the prefix ber- added to a root word often turns it into an intransitive verb that describes doing that action by oneself. So bisik on its own is the noun “whisper,” and berbisik is the verb “to whisper.”

You can form two related verbs:

• berbisik (intransitive) “to whisper” + kepada “to” + -nya enclitic pronoun “him/her.”
• membisikkan (transitive) “to whisper (something) to someone,” which requires a direct object (what you whisper) and a preposition for the person.

In our sentence, there’s no direct object being named (we don’t say what exactly was whispered), so berbisik kepadanya is more natural. If you wanted to mention the secret itself, you might say Saya membisikkan rahasia itu kepadanya.

bahwa is a subordinating conjunction meaning that. It introduces the content of the whisper, linking the main clause (Saya berbisik kepadanya) to the subordinate clause (agenda hari ini sangat padat). In formal Indonesian, you almost always use bahwa to introduce reported speech or thoughts.

In Indonesian, modifiers of a noun—whether they’re time phrases or adjectives—typically follow the noun. Here agenda hari ini is a noun phrase meaning today’s schedule or the agenda of today. Placing hari ini right after agenda makes it clear that “today” is describing which agenda.

Adjectives in Indonesian normally follow the noun they modify. padat means “dense” or “packed,” and sangat is an intensifier meaning “very.” So agenda hari ini sangat padat literally reads “the agenda of today [is] very packed.” Putting sangat padat at the end completes the clause by describing the state of the agenda.