how can i use“ 去了”and " 去过"

V+了：past tense 他去了北京
V+过：present perfect 他去过北京

2021年的那时候，我在动物园看过熊猫🐼。have been - 看过
昨天我去了动物园 看了熊猫🐼。V+了- past

A: Have you ever eaten a mango? 你吃过芒果吗？
B : I have. 我吃过芒果。

A : Have you eaten? 你吃了吗？
B：I ate mango. 我吃了芒果。

吃了是過去做的事或完成的事。我昨天吃了一個芒果。吃過是更接近經驗分享做過的事情。我在美國吃過芒果冰。

过：What this expresses is that the verb has been done at least once before, without specifying a particular time. 过 (guo) is used to talk about whether something has ever happened - whether it has been experienced.
了：The particle 了 (le) has a lot of uses. One of the most common is to express the completion of an action. This is called aspect, which is not the same as tense. With regards to 了 (le), aspect is about whether the action is complete in a certain time frame.
Examples:
nǐ xué ɡuò zhōnɡ wén mɑ ？ Have you ever studied Chinese?
你 学 过 中 文 吗 ？ Have you ever studied Chinese?
nǐ jiàn ɡuò nà ɡè rén mɑ ？ Have you seen that person before?
你 见 过 那 个 人 吗 ？ Have you seen that person before?
nǐ qù nǎ lǐ le ？ wǒ qù chāo shì le 。
你 去 哪 里 了 ？ 我 去 超 市 了 。
nǐ qù chāo shì zuò shén me le ？ wǒ qù chāo shì mǎi mánɡ ɡuǒ le 。
你 去 超 市 做 什 么 了 ？ 我 去 超 市 买 芒 果 了 。
Where have you been? I went to the supermarket.
Where have you been? I went to the supermarket.
What were you doing at the supermarket? I went to the supermarket to buy mangoes.
What were you doing at the supermarket? I went to the supermarket to buy mangoes.
nǐ zuó tiān chī mánɡ ɡuǒ le mɑ ？ wǒ zuó tiān méi chī mánɡ ɡuǒ ， wǒ jīn tiān chī mánɡ ɡuǒ le 。 zhè shì wǒ dì yí cì chī mánɡ ɡuǒ ， tài hǎo chī le 。 wǒ yǐ qián cónɡ lái méi chī ɡuò mánɡ ɡuǒ 。
你 昨 天 吃 芒 果 了 吗 ？ 我 昨 天 没 吃 芒 果 ， 我 今 天 吃 芒 果 了 。 这 是 我 第 一 次 吃 芒 果 ， 太 好 吃 了 。 我 以 前 从 来 没 吃 过 芒 果 。
nǐ chī ɡuò mánɡ ɡuǒ mɑ ？
你 吃 过 芒 果 吗 ？
wǒ méi chī ɡuò mánɡ ɡuǒ ， wǒ chī ɡuò pínɡ ɡuǒ 。
我 没 吃 过 芒 果 ， 我 吃 过 苹 果 。
nǐ qù ɡuò zhōnɡ ɡuó mɑ ？ wǒ yǐ qián qù ɡuò zhōnɡ ɡuó 。
你 去 过 中 国 吗 ？ 我 以 前 去 过 中 国 。
Have you ever been to China? I've been to China before.
Have you ever been to China? I've been to China before.
nǐ shànɡ ɡè yuè qù zhōnɡ ɡuó le mɑ ？ shì de ， wǒ shànɡ ɡè yuè qù zhōnɡ ɡuó le 。
你 上 个 月 去 中 国 了 吗 ？ 是 的 ， 我 上 个 月 去 中 国 了 。
Have you ever been to China? I've been to China before.
Did you go to China last month? Yes, I went to China last month.

Subtly, in the meaning aspect, it depends on what the other party asks or wants to know. 我吃过芒果，maybe the other party is asking what you have eaten.我吃了芒果，maybe the other party is asking you whether you have eaten.