Can't I just use "faham"?
The correct spelling is "paham", but it's an intransitive verb, so you'll have to use "tentang" or "akan" after it. Saya belum paham tentang fungsi itu.
Oh thanks for the explanation :)
I didn't know it's spelled with p, because in Malaysian they spell it with f I think.
And in Jakarta they say "ngerti" instead of "mengerti".
Is that a real word or just slang?
"Ngerti" (and other words with the prefix ng- and nge-) is from the Betawi language, the ethnic group living in and around Jakarta.
Mengerti is better for understood. Paham is know.
I use "mengerti" and "paham/memahami" mostly interchangably. For "know", we usually use "tahu/mengetahui".