The number of masks in our house is going down little by little.
My son keeps forgetting masks everywhere, so we don't have as many around the house anymore.
ーThe number of masks in our house is going down little by little.
「家のマスクの数がだんだん減っていっている」
the number of ... で「…の数」
to go down で「減る・減少する」
little by little で「少しずつ・だんだん」
ーMy son keeps forgetting masks everywhere, so we don't have as many around the house anymore.
「息子があちこちでマスクを忘れてくるから、もう家にあんまりマスクがない」
to forget masks everywhere で「あちこちでマスクを忘れる」
ご参考まで！
カナダ 
