Prepositions – Meaning Differences: ‘In the Job’, ‘On the Job’, ‘At the Job’

Reasonable means that whatever decision was made is appropriate given the particular circumstances, and most would regard it as so.

Justified means that whatever decision was made is done for a good reason, in the interest of fairness.

There are times the words could be used interchangeably, and contexts where the difference is subtle. It all depends on the nature of the request or issue at hand.

I might use "justified" if I was angry about something, and was acting in response:

Was it polite to skip their wedding after they insulted me like that? No, but I think my decision was justified.

I might use "reasonable" if I think everyone would agree that there was nothing else that could be done:

Was I happy about missing their wedding so that I could go to my mother's funeral? No, but I think my decision was reasonable.

But there are contexts where either word will work just fine:

You said that you'd deliver the cake before noon, but it didn't get here until 3 o'clock. I think my request for a refund is reasonable/justified.

In that sentence, reasonable would work because most people would agree that a refund would be appropriate given the circumstances, and justified would work because the request is fair.

It depends on a context. They both may mean the same thing in example like this -

He can hardly write = He can barely write

But then, if you check all the meanings for both the words, you may come up with an example where the words cannot be interchanged.

Now, when in case where hardly refers to 'almost never', replacing it with barely may not sound natural.

"I hardly go for a social gathering" over "I barely go for..."

Edit after the question is edited:

Yes, I agree with djechilin (+1), use poorly or badly instead. The book is poorly translated.