1. We know that when you add “了” after a verb, it indicates that this action happened at some time in the past, like“我吃了火锅” just means “ I ate a hotpot.” In this sentence, you can also put “了” after the object, to say “我吃火锅了” It’s absolutely the same as “我吃了火锅” They have the same meaning.
But when the object of the verb is quantified, like “I ate hotpot three times,” you can only say “我吃了三次火锅” Like:
“上个星期，我吃了三次火锅 – I ate hotpot three times last week.”
“去年五月，我吃了三次火锅 – I ate hotpots three times last May.”
It’s typical past tense, the same as in English.
The negative: “我没吃火锅。”“上个星期，我没吃火锅。”
2. When you talk about your past experiences, you need to add “过” after the verb, like
“我吃过臭豆腐。 – I’ve ever eaten stinky tofu before. ”
“我去过南极。 – I’ve been to the South Pole before.”
When the object is quantified, like “I’ve eaten hotpot three times” you can say “我吃过三次火锅。” It still shows your experiences; it means that you’ve only ever eaten hotpot three times in your lifetime.
The negative: “我没吃过火锅。”
3. But if you want to say “I’ve eaten hotpot three times from the first time I’d eaten it up to now,” you need to say “我吃了三次火锅了。” It’s like the perfect progressive in English. It means from the first time you eat hotpot, up to the moment you’re speaking, you’ve eaten hotpot three times.
So from a point in time in the past, up to the moment of speaking, you have done something for many times, you can use this structure, like “这个月，我吃了三次火锅了。- I’ve eaten hotpot three times this month.” It means from the beginning of this month up to the moment you are speaking, you’ve eaten the hotpot three times.
And from a point in time in the past up to the moment of speaking, you have been doing something fora period of time, you can still use this structure, like in English: “I’ve been learning Chinese for three years,” can also be translated into “我学了三年汉语了。” It means from the first time you started learning Chinese up to the moment of speaking, you’ve been learning Chinese for three years.
I ate hotpot at noon. 中午，我吃火锅了。
It’s my first time to eat hotpot. 这是我第一次吃火锅。
I’ve never eaten the hotpot before. 我以前没吃过火锅。
Have you ever eaten hotpot? 你吃过火锅吗？
I’ve eaten the hotpot many times. 我吃过很多次火锅。
I’ve already eaten the hotpot three times this month.