[General] He can't hack it.

[Silverobama]

Hi teachers.

If someone can't do one thing, I wonder if I can say "He can't hack it". For example, my cousin always plays computer games and watches movies online; he doesn't want to do anything but he wants the money. Someone who doesn't know my cousin suggests that my cousin might have a try and I say to someone "He can't hack it".

Is it natural? Or maybe it's natural but not in my context.

 

[GoesStation]

When someone can't hack something, it means the thing was too difficult — often in an emotional sense. The expression doesn't suit your scenario without more context.

Note that this is a slangy expression that's not suited to formal writing.

 

[emsr2d2]

For example, my cousin always plays computer games and watches movies online; he doesn't want to do anything but he wants the money. Someone who doesn't know my cousin suggests that my cousin might have a try and I say to someone "He can't hack it".

I don't understand your example.

1. You can't say he doesn't want to do anything when you've made it clear that what he wants to do is play computer games and watch movies.
2. What do you mean by "but he wants the money". The money for what? Or did you just mean that he wants money (no article), meaning he wants to be paid (by someone) even though he doesn't want to work.
3. What do you mean by "suggests that my cousin might have a try"? Have a try at what?

 

[Silverobama]

I don't understand your example.

1. You can't say he doesn't want to do anything when you've made it clear that what he wants to do is play computer games and watch movies.
2. What do you mean by "but he wants the money". The money for what? Or did you just mean that he wants money (no article), meaning he wants to be paid (by someone) even though he doesn't want to work.
3. What do you mean by "suggests that my cousin might have a try"? Have a try at what?

He just wanted to play computer games and besides doing nothing. He wants money to live and to survive. A friend of mine didn't know my cousin well and he asked me to help my cousin to find a job. I actually tried to help him many times but he didn't end up doing any of those jobs well. So when this friend suggested "Maybe you cousin can have a try to work here/to get this job, I said "He can't hack it".

 

[emsr2d2]

He just wanted to play computer games and, besides that, [STRIKE]doing[/STRIKE] do nothing.

He [STRIKE]wants[/STRIKE] wanted money to live on. [STRIKE]and to survive.[/STRIKE]

A friend of mine, who didn't know my cousin well, [STRIKE]and he[/STRIKE] asked me to help my cousin to find a job.

I had actually tried to help him many times but he didn't end up doing any of those jobs well.
You need to reword the underlined part. We didn't even know he had had a job before. You said only that you had tried to help him find a job before.

So when this friend [STRIKE]suggested[/STRIKE] said "Maybe your cousin can [STRIKE]have a[/STRIKE] try [STRIKE]to[/STRIKE] working here/to get this job, I said "He can't hack it".

Note my corrections (in red) and comments (in blue) above. That would have been a much better explanation than the one you gave in post #1.

In BrE, you might just about be able to use "hack it" if you change the idea somewhat.

Friend: I saw a job vacancy advertised at the local supermarket earlier. Maybe your cousin could apply?
You: My cousin? Work for a living? He couldn't hack it!