difficult to加什么词?

1. It was difficult to calm my brother down.
要使我弟弟平静下来是很困难的。

2. It is difficult to keep order in this town.
要维持这个城镇的治安(秩序)是困难的.

3. English is a language easy to learn but difficult to master.
英语是一门学起来容易但是难以精通的语言。

后面应加动词原形 例如：it is difficult to finish the task.

It's difficult （for sb.)to do ...对某人来说，做...很难

举个例子:
It's difficult for me to speak Japanese.
多我来说，说日语很难。本回答被提问者采纳

他能跟to 吗