Wenn ich viel Arbeit habe, hilft mir meine Tochter im Haushalt.

Because wenn introduces a subordinate clause. In German subordinate clauses, the conjugated verb usually goes to the end.

So:

• Wenn ich viel Arbeit habe = When/If I have a lot of work

Compare that with a main clause:

• Ich habe viel Arbeit.

In the main clause, habe is in the normal second position.
In the wenn clause, it moves to the end.

German normally uses a comma to separate a subordinate clause from a main clause.

So the sentence is divided like this:

• Wenn ich viel Arbeit habe,
• hilft mir meine Tochter im Haushalt.

That comma is required in standard German.

Wenn can mean both if and when, depending on context.

In this sentence, it usually means something like:

• When I have a lot of work
• Whenever I have a lot of work
• sometimes also If I have a lot of work

So wenn is often used for repeated or general situations.
If the idea is every time this happens, wenn is very natural.

German main clauses follow the verb-second rule. The conjugated verb must come in the second position.

Here, the first position is taken by the whole subordinate clause:

• Wenn ich viel Arbeit habe = position 1

So the verb in the main clause must come next:

• hilft = position 2

Then the rest follows:

• mir meine Tochter im Haushalt

That is why you do not say:

• Wenn ich viel Arbeit habe, meine Tochter hilft mir im Haushalt.

That would sound wrong in standard German.

Because the verb helfen takes the dative case, not the accusative.

So:

• jemandem helfen = to help someone

Examples:

• Sie hilft mir. = She helps me.
• Ich helfe dir. = I help you.
• Wir helfen ihm. = We help him.

So in your sentence:

• mir is dative
• mich would be wrong with helfen

Because meine Tochter is the subject of the main clause, and the subject is in the nominative case.

In the main clause:

• meine Tochter = the one doing the helping
• mir = the person receiving the help

So:

• meine Tochter = nominative
• mir = dative

That is why the forms are different.

Because Arbeit here is being used as an uncountable noun, similar to work in English.

So German says:

• viel Arbeit = a lot of work

But with countable plural nouns, you use viele:

• viele Bücher = many books
• viele Aufgaben = many tasks

So think of it like this:

• viel
  • uncountable/singular idea
• viele
  • countable plural nouns

Here Arbeit means work, not job in the sense of a specific profession.

So:

• viel Arbeit haben = to have a lot of work / to be very busy

If you want to talk about a person’s job, Arbeit can sometimes refer to that too in everyday speech, but in this sentence it clearly means a lot of work to do.

Im Haushalt means in the household or more naturally in English, around the house or with household chores.

It comes from:

• in dem Haushalt → im Haushalt

So the sentence means that the daughter helps with things connected to running the home, for example:

• cleaning
• cooking
• laundry
• other household tasks

Because im is the normal contraction of:

• in dem → im

German often contracts certain preposition + article combinations:

• in dem → im
• an dem → am
• zu dem → zum
• zu der → zur

So im Haushalt is just the natural shortened form of in dem Haushalt.

Both are possible.

German word order is more flexible than English, especially with pronouns. In this sentence, mir often comes early because short pronouns are frequently placed before fuller noun phrases.

So these are both possible:

• Wenn ich viel Arbeit habe, hilft mir meine Tochter im Haushalt.
• Wenn ich viel Arbeit habe, hilft meine Tochter mir im Haushalt.

The version with mir earlier sounds very natural because:

• mir is a short pronoun
• German often places such pronouns before longer noun phrases

So the original sentence is a very normal word order pattern.

Because the subject is meine Tochter, which is singular.

So the verb must agree with that subject:

• meine Tochter hilft
• meine Töchter helfen

Even though there are several other words in the sentence, the verb agrees only with the subject meine Tochter.

Yes, absolutely. Wenn ich viel zu tun habe is very common and often sounds especially natural in everyday German.

Compare:

• Wenn ich viel Arbeit habe = When I have a lot of work
• Wenn ich viel zu tun habe = When I have a lot to do / When I’m very busy

Both are correct, but viel zu tun haben is one of the most common everyday ways to express this idea.

Most naturally, it sounds like a general or repeated situation:

• Whenever I have a lot of work, my daughter helps me around the house.

That is because wenn often introduces habitual or repeated events.

If you wanted to refer to one specific past occasion, German would usually use a different structure or more context.

Yes. You can say:

• Meine Tochter hilft mir im Haushalt, wenn ich viel Arbeit habe.

That means the same thing.

The difference is mostly one of focus:

• Starting with Wenn ich viel Arbeit habe puts the condition or situation first.
• Starting with Meine Tochter hilft mir im Haushalt puts the main information first.

Both are correct and natural.