英语求助we are having piano lesson next Friday 是什么句式为什么加ing一般将来时

we are all having a good time中的hveing为什么加ing? we are having an English lesson. I will have a piano lesson next Friday Lily told me swimming lesson为什么swim要加ing we are busy (preparing )our lesson these days括号中为什么填ING形式 an we having are lesson english 连词成句 英语课本里They are having a Music lesson"music"里的“m”为什么要大写 My piano lesson finishes at three.为什么finish加es 英语被动语态一般将来时句式是什么谢谢 They are comfortable having Chinese food中have为什么要加ing The students are having a PE lesson.为什么要用（are having）? l go to the piano lesson on mondy and friday .