kono sigoto ha kurou ga ooi.

This is very common in Japanese.

• この仕事は sets the topic: as for this job ...
• 苦労が多い says something about that topic: there are many hardships / it involves a lot of hardship

So the structure is roughly:

[Topic] は [subject inside the comment] が + description

In other words, この仕事 is the overall thing being talked about, while 苦労 is the thing that is specifically described as being 多い.

A natural breakdown is:

• この仕事は = as for this job
• 苦労が多い = the hardships are many

This kind of double marking is normal in Japanese.

Because 苦労 is the thing being described by 多い.

With が, the sentence simply states that, within the topic of this job, hardship is plentiful.

If you said 苦労は多い, it would sound more contrastive, like:

• Hardship is plentiful, but ...
• As for hardship, there is a lot of it

So が is the more neutral choice here.

Very roughly:

• 苦労が多い = there is a lot of hardship
• 苦労は多い = hardship, at least, is a lot / there’s a lot of hardship (in contrast to something else)

Yes. 多い is an i-adjective, and it is often used with nouns that represent things that can occur in large numbers or frequency.

So 苦労が多い literally feels like:

• hardships are many
• there is much hardship
• there are many struggles

Even though English may use a noun phrase like a lot of hardship, Japanese often uses X が多い very naturally.

Other similar patterns:

• 問題が多い = there are many problems
• ミスが多い = there are many mistakes
• 残業が多い = there is a lot of overtime

苦労 means hardship, trouble, difficulty, or struggle, especially the kind you go through over time.

It is not just one tiny inconvenience. It often suggests:

• effort
• stress
• difficulty
• things being tough to deal with

So この仕事は苦労が多い does not just mean the job is slightly annoying. It suggests that the job involves many difficulties or a lot of struggle.

Because this sentence is describing the job by saying that hardship is abundant in it, not directly saying someone struggles.

Compare:

• この仕事は苦労が多い。
  = This job involves a lot of hardship.

• この仕事は苦労する。
  = This job struggles.
  This sounds wrong, because the job is not the one doing the struggling.

If you want to say people struggle with this job, you could say something like:

• この仕事は苦労することが多い。
• この仕事は苦労が多い仕事だ。
• この仕事では苦労することが多い。

But the original sentence is a compact way to say that the job comes with many difficulties.

Japanese nouns usually do not mark singular vs. plural the way English does.

So 苦労 can be understood as:

• hardship in general
• many hardships
• a lot of struggle

The context tells you how to understand it.

That is why 苦労が多い can naturally mean there are many hardships even though 苦労 itself does not change form.

Yes. That would be the polite version.

• この仕事は苦労が多い。 = plain style
• この仕事は苦労が多いです。 = polite style

The meaning is basically the same. The difference is just tone and level of formality.

Because この仕事 is the topic, marked by は, not a location or target.

The sentence is not saying in this job in a grammatical location sense. It is saying:

• As for this job, ...

That is why は works well.

If you wanted to emphasize in this job, you could say:

• この仕事では苦労が多い。

That version makes the setting a little more explicit: In this job, there is a lot of hardship.

So:

• この仕事は苦労が多い = As for this job, there is a lot of hardship
• この仕事では苦労が多い = In this job, there is a lot of hardship

Both are possible, but the original is very natural.

この means this, and it directly modifies 仕事.

So:

• この仕事 = this job

Remember:

• この + noun
• その + noun
• あの + noun

You cannot say just この by itself before a pause if you mean this job. It must attach to a noun.

So この仕事 is one unit.

Yes, but the nuance is different.

• この仕事は苦労が多い。
  = This job involves many hardships / a lot of struggle.

• この仕事は大変だ。
  = This job is tough / this job is hard.

大変だ is broader and more general.
苦労が多い focuses more on the many difficulties or struggles involved.

So the original sentence feels a bit more specific and vivid.

Yes, that is understandable, but it sounds a little different.

• 苦労が多い is compact and very natural.
• 苦労がたくさんある also means there is a lot of hardship, but it sounds a bit more explicit, almost like there exist many hardships.

In many cases, Japanese prefers X が多い for this kind of idea.

So the original sentence is a very natural way to say it.

They are:

• この = kono
• 仕事 = しごと (shigoto)
• は = pronounced wa
• 苦労 = くろう (kurō)
• が = ga
• 多い = おおい (ōi)

So the full sentence is read:

この しごとは くろうが おおい。

Yes, that is a good literal way to think about it.

A literal breakdown is:

• この仕事は = as for this job
• 苦労が = hardships / hardship
• 多い = are many

So literally: As for this job, hardships are many.

That literal understanding can help you see how the grammar works, even if the natural English translation is something like:

• This job involves a lot of hardship.
• There are many difficulties in this job.
• This job is full of struggles.