If you are just going to delete them after, don't send them in the first place.
If you are just going to erase your messages afterwords, don't bother sending them to me at all.
ーIf you are just going to delete them after, don't send them in the first place.
「後で消すなら、最初に送ってこないで」
to delete で「削除する・消す」
in the first place で「そもそも・最初に」
ーIf you are just going to erase your messages afterwards, don't bother sending them to me at all.
「後からメッセージを消すなら、そもそも私に送ってこないで」
to erase で「消す・削除する」
afterwards で「後に」
at all で「そもそも」
ご参考まで！
Don't send the message in the first place if you're going to delete it.
ご質問ありがとうございます。
「〜しないで」と言いたいときは、Don't を使って表現することが出来ます。
Don't send the message in the first place if you're going to delete it.
「結局そのメッセージを消すなら、最初から送らないで」
他にも表現方法はございますので、ご参考までに。
カナダ 
日本 
