It is difficult for me to remember the sentences and repeat after you.
The sentences are too long to retain and repeat.
It is hard for me to retain and repeat the sentences because each of them is too long.
覚える、や(頭の中に)保持する、をRememberやRetainと言います。
Retain して Repeatするのが、 each of the sentences is too long.(文章それぞれが長すぎる)から、difficult for me (私にとって難しい)、となります。
The sentences are too long to retain and repeat.
文章が長すぎて覚えて繰り返しできない。
It is hard for me to retain and repeat the sentences
覚えてリピートすることが私にとって難しい
because each of them is too long.
なぜなら 1文が長すぎる。