The given sentence does not have any punctuation. Choose the correctly punctuated version. dont you understand what im saying shouted his father get down at once

The father's words form a direct question, so the quoted part ends with a question mark inside the quotes ('...saying?'), followed by the reporting clause and a new quoted sentence 'Get down at once.' Only the version '"Don't you understand what I'm saying?" shouted his father. "Get down at once."' has quotation marks, the question mark and correct apostrophes in don't/I'm.