I remember we discussed it, but I forgot the details
Sorry, I don't really remember
I remember =(私は)覚えてる
I remember we discussed it, but I forgot the details =それについて話したのは覚えているけど、詳細は忘れちゃった
discuss =話し合う
details =詳細
Sorry, I don't really remember =ごめん、あまり覚えていない
Good luck!