What is user's actual pain?

I think you need a medical degree.

@Katakompe no... I don't want overspent money....

That job offer is a translation. But definitely not from Mandarin, because then it would be way worse.

Looks to me like someone wants to expand into China (well, who doesn't) and needs at least one dev who can extract (or better extort) information about the actual needs from the chineese customers.
Computer languages and experience probably don't really matter - if you are able to blend into the chineese culture where it is way harder than in western cultures to get meaningful information about what people actually want and need.
If diplomacy isn't your thing, don't apply.

And their main product definitely is an Oracle-based Java application that is in dire need of care. So that might be a red flag too...

Other languages: English, Chinese

So what's the native language?

@Oktokolo erm I'm Chinese actually.

@donuts I am from Malaysia, Malay is the native language here.

@Oktokolo I just don't know why in my country have weird jobs like this...

@Oktokolo well, it could be translating from Mandarin... by a human who doesn't speak English natively

Maybe the previous projects caused a lot of pain to your users and they want to avoid them now

E.g meaningless errors or popups, back button issues, poor UX, or too slow an app

Well the resume listed Oracle so I'm sure they fully understand what pain is.

I think they mean a user's stupidity

The users actual pain is that great technologies for sharing data exist, but they’re still stuck using fax machines for all but one of their vendors.