YOU SAID:

bridges are very hard to build and are difficult to maintain

INTO JAPANESE

橋は建設するのが非常に難しく、維持するのが難しいです

BACK INTO ENGLISH

Bridges are very difficult to build and difficult to maintain

INTO JAPANESE

橋は建設が非常に困難で維持が困難です

BACK INTO ENGLISH

Bridges are very difficult to build and difficult to maintain