From the Days of Eternity
Jesus is a created being who has existed for a very long time, but he had
a beginning. He is not eternal in the way Jehovah is.
Read and note the Hebrew word olam (eternity). This is the same word used in for Jehovah's eternality — "from everlasting to everlasting, you are God." If olam means true eternity for Jehovah, it means true eternity for the Messiah. The NWT weakens "from eternity" to "from ancient times" — ask why the same Hebrew word gets different translations when applied to Jehovah versus Jesus. Pair with where the Messiah is called "Eternal Father" — another olam reference.
The same Hebrew word describes both Jehovah's and Jesus' eternality. The NWT translates it differently for each — that's theology disguised as translation.
Olam can mean 'a long time' — it doesn't always mean eternity
Then would only mean Jehovah has existed "a long time" too. If you accept olam as true eternity for Jehovah, consistency requires you accept it for the Messiah. The word doesn't change meaning based on who it describes.
Don't get into an extended Hebrew debate. Keep the comparison simple: same word, same meaning, different persons. Let the consistency argument do the work.
Read with the verses around it until you can quote it from memory, then read and . Compare the NWT's 'from ancient times' in with how it renders , so you can show that the same Hebrew word, olam, is translated differently for the Messiah than for Jehovah. Practise the doorstep question aloud, keeping the comparison simple: same word, same meaning, different persons. Expect 'olam can just mean a long time'; rehearse the consistency reply, that if olam means true eternity for Jehovah in , it cannot shrink when it describes the Messiah, without being drawn into an extended Hebrew debate.