Your dialogue is stiff because everyone is being too honest
Great dialogue can come from radical emotional honesty. But in most real conversations, people
dodge questions
answer indirectly
lie (badly)
change the subject
crack jokes to avoid serious answers
lie (convincingly)
say half of what they mean
tell the truth but get so anxious/angry/defensive others now think they're lying
If your dialogue feels unnatural, it might be because everyone is saying exactly what they think, or articulating their thoughts too well. Try letting characters hide things instead.
Subtext is where tension lives.
more so,
people don’t always speak in full sentences,
slang can change depending on age range, demographic, etc. &
don’t be scared of vocal pauses (uhm, uh, err)
