Question

什么时候用to+have什么时候用are+having？

Answer 1

问题应该改为 什么时候用 have 什么时候用having。to have 和have是一个场景。
1、通常用have的场景
a、表达你拥有或取得某物。
I have a new car. (我有一辆新车)
b、表达常态或习惯。
I have breakfast at 7 every morning. (我每天早上7点吃早饭)
2、通常用having的时候
a、表达正在进行的动作或临时状态。
We are having a party tonight. (我们今晚在开派对)
I’m having trouble finishing my homework. (我正在有困难完成家庭作业)
b、用于进行体表现正在发生的变化或动作。
The company is having financial difficulties recently. (最近该公司正在经历财务困难)
My son is having a growth spurt now. (我儿子现在正在快速长个儿)
3、两者可以通用互换的场景
用于现在完成时,表达刚刚结束的动作
I have / am having just finished my work. (我刚完成工作)
We have / are having already had dinner.(我们已经吃过晚饭了)
4、除此之外,在特定的习语表达中也有have或are having的惯用法,这需要在使用中逐渐熟悉和记忆。

Answer 2

are having 是现在进行时态

to have 是动词不定时式

要根据具体句子意思与语境
如
Look, they are having breakfast.

I want to have breakfast.