היא נשארה בבית במקום ללכת לקניון, כי הייתה לה עוד משימה אחת.

Because the subject is היא = she.

In the past tense, Hebrew verbs agree with the subject in gender and number:

• הוא נשאר = he stayed
• היא נשארה = she stayed

So נשארה is the correct past-tense feminine singular form of להישאר (to stay / to remain).

Here it most naturally means at home.

Literally, בבית is in the house / at home, and context decides which English translation sounds best. In this sentence, since the contrast is with going to the mall, at home is the most natural choice.

Also, בבית is made of:

• ב־ = in / at
• הבית = the house / the home

After certain prepositions, the ה of the is absorbed, so:

• ב + הבית → בבית

Yes—by itself, מקום means place. But the expression במקום can also mean instead of.

So in this sentence:

• במקום ללכת לקניון = instead of going to the mall

This is a very common Hebrew pattern:

• במקום + infinitive
• meaning instead of doing something

Examples:

• במקום ללמוד, הוא ישן = instead of studying, he slept
• במקום לדבר, תכתוב = instead of talking, write

Because Hebrew often uses במקום + infinitive to mean instead of doing something.

ללכת is the infinitive to go. So:

• במקום ללכת = instead of going

This is similar to English instead of going, though Hebrew uses the infinitive form with ל־.

They are doing two different jobs.

1. ללכת

   • This is the infinitive form to go
   • The ל־ here is part of the infinitive

2. לקניון

   • This means to the mall
   • Here ל־ is the preposition to

So:

• ללכת = to go
• לקניון = to the mall

Also, לקניון comes from:

• ל + הקניון = to the mall

The ה of the disappears after the preposition, so ל + הקניון becomes לקניון.

Because Hebrew does not usually use a normal verb meaning to have the way English does.

Instead, Hebrew commonly expresses possession with a structure that literally works like:

• there was / there is ... to her

So:

• יש לה משימה = she has a task
• הייתה לה משימה = she had a task

Literally, הייתה לה עוד משימה אחת is something like:

• there was to her one more task

But in natural English, we simply say:

• she had one more task

Because היה / הייתה agrees with the thing possessed, not with the person who possesses it.

The thing she had is:

• משימה = task

And משימה is feminine singular, so Hebrew uses:

• הייתה לה משימה = she had a task

Compare:

• היה לה ספר = she had a book
  (ספר is masculine singular)
• הייתה לה משימה = she had a task
  (משימה is feminine singular)

This is a very important Hebrew pattern.

Because Hebrew often leaves out subject pronouns when they are already clear from the verb or from context.

So:

• כי הייתה לה עוד משימה אחת

already clearly means:

• because she had one more task

Adding היא is possible in some contexts, but it is usually unnecessary here and can sound more marked or emphatic.

It means one more task or another task.

Breakdown:

• עוד = more / another / additional / still
• משימה = task
• אחת = one

So the phrase literally is:

• another one task

But in natural English, that becomes:

• one more task
• another task

In this sentence, one more task fits especially well.

Because in Hebrew, the number one usually comes after the noun:

• ילד אחד = one boy
• ילדה אחת = one girl
• משימה אחת = one task

Since משימה is feminine, the form of one must also be feminine:

• masculine: אחד
• feminine: אחת

So משימה אחת is the correct form.

Here it means another / one more.

עוד can mean different things depending on context:

• עוד פעם = again / one more time
• עוד קפה = more coffee / another coffee
• אני עוד עובד = I am still working

In עוד משימה אחת, it means:

• one more task
• another task

Very often, yes. In this sentence, כי clearly means because:

• כי הייתה לה עוד משימה אחת = because she had one more task

In some contexts, כי can also have other functions in more formal or literary Hebrew, but for everyday modern Hebrew, because is the most important meaning to know.

The sentence is structured like this:

• היא נשארה בבית = she stayed at home
• במקום ללכת לקניון = instead of going to the mall
• כי הייתה לה עוד משימה אחת = because she had one more task

So the full order is:

subject + verb + place + instead-of phrase + reason clause

This is a very normal and natural Hebrew sentence structure.