YOU SAID:

My last birthday party went so bad that we all died and my grandpa fell into the river

INTO JAPANESE

私の最後の誕生日パーティーが腐ったので、我々 はすべてが死亡し、私のおじいちゃんが川に落ちた

BACK INTO ENGLISH

My last birthday party was bad, so we are all but dead and my grandfather fell into the river

INTO JAPANESE

私の最後の誕生日パーティーが悪かったので、私たちはすべてが死んだと私の祖父は、川に落ちた

BACK INTO ENGLISH

Since my last birthday party was bad, we all died and my grandfather fell into the river