if benar means correct and kah means it is wouldn't this translate to is it correct?
kah is indicating a question "Right?" so you you could also say "Is that right?"
Thanks
Benarkah = Betulkah?
banar is true betul is good
Really? = sungguh? Or in informal way we normally say "beneran?" It's the same as "benarkah?"
Serious? = serius? Seriusan?
Why is "Truly?" not accepted?
it's more synonymous to "very" rather than "right/true" in this context.
I found this explanation https://www.quora.com/According-to-Indonesians-whats-the-difference-between-betul-and-benar-and-if-it-has-the-same-meaning-then-why-are-kebetulan-and-kebenaran-totally-different#:~:text=Benar%20means%20it%20is%20not,able%20to%20use%20it%20correctly.
Is "Right?" ok?
Yes.
Correct?