My dog is loosing it so he forgets where to go to the bathroom.
My dog is getting old and senile and can't remember where he used to go to the bathroom.
この場合、次のような言い方ができますよ。
ーMy dog is loosing it so he forgets where to go to the bathroom.
「うちの犬がボケてきて、トイレに行く場所を忘れてしまう」
my dog is loosing it はスラングでボケてきていることを言えます。
ーMy dog is getting old and senile and can't remember where he used to go to the bathroom.
「うちの犬は歳でもうろくしてきて、どこでトイレをしていたか思い出せない」
to get senile で「もうろくする・ボケる」と言えます。
ご参考まで!
Our dog is getting old and has started to become forgetful.
He no longer goes to the bathroom in his designated spot.
ご質問ありがとうございます。
・「Our dog is getting old and has started to become forgetful. 」
(意味) 我が家の犬が高齢となり、ボケてきた。
<例文>Our dog is getting old and has started to become forgetful. He no longer goes to the bathroom in his designated spot.
<訳>我が家の犬が高齢となり、ボケてきた。 決まったところでトイレをしなくなった。
参考になれば幸いです。