I thought you weren't going to send any more pointless messages on LINE.
I thought you were done sending pointless messages on LINE.
I thought you weren't going to send any more pointless messages on LINE.
I thought you were done sending meaningless messages on LINE.
くだらない=pointless, meaningless
ラインを送る=send messages on LINE
ラインを送るという職役を英語ですることはできませんので、ラインでメッセージを送ると言い換えました。