verb + 过 = result 看过 = have seen 去过= have been / have gone 听过 = have heard

actually this is the most compliated question you can ask about chinese grammar. you can write a paper about it. 过 is easier to use than 了. not to discourage you but even many "Chinese experts" are not able to use 了 as natural as a native speaker does. the most practical way to learn it is to learn by examples. find as many examples as you can and try to "feel" what it actually means. I wanted to explain to you theoretically but I find that it takes my grammar book 40 pages to explain 了 and 过. so I think I'll pass. but intuitively, 过 is more like "have done" and 了 is more like "did". I remember a article that says 80 percent of the time 了 will be translated into simple past tense instead of perfect tense. "verb + 过" usually has something to do with what you are talking about right now. it not only describs sth that has happend, it relates to now. in contrast, 了 only descripes that "sth happened" or in other words, "the situation changed". an important and maybe confusing thing to notice is that 过 actually has two functions. it can be an auxiliary as discussed above. it can also work as a complement. when used as a complement, it means you have finished sth., and can usually be replaced with 完. for example, -你昨天让我看的那本书，我看过了，很有趣。 The book you asked me to read yesterday, I have read it, it's interesting. here 看过了 can be replaced with 看完了. compare with -看一下这本书吧，很有趣。 Read this book, it's quite interesting. -这本书我看过。 I've read this book before. in the first example, you can also see the use of 了. let's say you finished the book exactly at 8 o'clock in the morning. then one second before 8, the situation is 没看完 (which means haven't finished yet, and here you can't replace 完 with 过 reversely), one second after 8, the situation becomes 看完了. 了 marks that the situation changes.

it's a marker of an expierenced action. so 看过 means have seen sth. 听说过 means have heard of sth. it's different from 听过, which means have listened to sth.

Ci provo anche io a spiegarlo. Il 了 indica semplicemente un'azione passata, conclusa. Il 过 indica fare l'esperienza descritta dal verbo. Provo con gli esempi. 我吃了饺子/ 我吃过饺子. Nella prima frase indico che (poco fa) ho mangiato i jiaozi cinesi, nella seconda indico che conosco il sapore dei jiaozi, so cosa sono perché ho provato a mangiarli. Il 过 perciò indica un "essere a conoscenza di qualcosa (per averla provata o vissuta in prima persona)". Nel caso della frase 听说过 significa "ne ho sentito parlare", "lo so" letteralmente: so che è stata detta.

In this case it just indicate a tense. indicating the action happed in the past A good thing in Chinese is that you don't need to change the word format BTW, it should be ‘听说过’