YOU SAID:

Doors are hard to open

INTO JAPANESE

ドアは開けにくい

BACK INTO ENGLISH

Doors are difficult to open

INTO JAPANESE

ドアを開けにくい

BACK INTO ENGLISH

It is difficult to open the door.

INTO JAPANESE

ドアを開けるのは難しいです。

BACK INTO ENGLISH

It is difficult to open the door.