אני שמה את המפתח בתיק לפני שאני יוצאת מהבית.

Because the speaker is female.

In the present tense, Hebrew verbs agree with gender and number:

• אני שם = I put (said by a male speaker)
• אני שמה = I put (said by a female speaker)

The same pattern appears later in the sentence:

• אני יוצא = I go out / leave (male)
• אני יוצאת = I go out / leave (female)

So this sentence is being said by a woman or girl.

Here, את is the direct object marker. It does not mean you in this sentence.

Hebrew uses את before a definite direct object—usually one with ה (the), a name, or something otherwise specific.

So:

• אני שמה את המפתח = I put the key
• המפתח is definite because it means the key

Compare:

• אני שמה מפתח = I put a key
• no את, because mafteaḥ is indefinite

So את is there because המפתח is a specific key.

This is because Hebrew has prefix prepositions.

The preposition ב־ means in and attaches directly to the noun:

• בתיק

If the noun is definite (the bag), then ב + ה + תיק combines into one form. In fully pointed Hebrew, you would see a pronunciation difference:

• בְּתיק = in a bag
• בַּתיק = in the bag

But in normal unpointed writing, both are written בתיק.

So in everyday Hebrew spelling, בתיק can mean either:

• in a bag
• in the bag

You usually know which one is meant from context or from the translation.

לפני ש־ means before followed by a full clause.

So:

• לפני = before
• שאני יוצאת = that I leave / that I go out

Put together:

• לפני שאני יוצאת מהבית = before I leave the house / before I leave home

This is a very common Hebrew pattern:

• אחרי שאני אוכלת = after I eat
• לפני שהוא מגיע = before he arrives

Literally, the ש־ is similar to that, but in natural English we usually do not translate it directly.

Because Hebrew present-tense forms do not show person clearly.

The form יוצאת tells you:

• feminine
• singular

But it does not tell you whether the subject is:

• I
• you (feminine singular)
• she

So אני is needed to make it clear:

• שאני יוצאת = that I am leaving / that I leave

Without אני, the sentence would sound incomplete or unclear in this structure.

The verb לצאת means to go out / to leave, and it normally goes with מ־ (from / out of).

So:

• יוצאת מהבית literally means
• goes out from the house

In natural English, that becomes:

• leave the house
• or often simply leave home

And מהבית breaks down like this:

• מ־ = from
• הבית = the house / the home

So:

• מ + הבית = מהבית

It can mean either, depending on context.

In this sentence, מהבית is very naturally understood as:

• from home
• or from the house

Hebrew often uses הבית where English would simply say home:

• אני בבית = I’m at home
• אני חוזרת הביתה = I’m returning home

So even though the Hebrew word is literally the house, the most natural English meaning is often home.

Yes, the verbs are in the present tense:

• שמה
• יוצאת

But in Hebrew, the present tense can describe:

• a habitual action
• a general routine
• something happening right now, depending on context

So this sentence could mean something like:

• I put the key in the bag before I leave home as a routine or usual action

If you wanted a clear past or future meaning, Hebrew would change the verbs:

• past: שמתי, יצאתי
• future: אשים, אצא

Yes. Hebrew word order is fairly flexible.

This sentence:

• אני שמה את המפתח בתיק לפני שאני יוצאת מהבית.

could also be said as:

• לפני שאני יוצאת מהבית, אני שמה את המפתח בתיק.

Both are natural. The difference is mostly about emphasis:

• starting with אני שמה... emphasizes the action of putting the key in the bag
• starting with לפני שאני יוצאת... emphasizes the time sequence: before I leave

Yes, it can be.

שמה can also be a separate word meaning something like there in some contexts, especially in more colloquial or non-standard speech. But here, it is clearly the verb puts because of the sentence structure:

• אני שמה את המפתח...

After אני, a present-tense verb makes perfect sense, and then את המפתח follows as the object. So here שמה is definitely the feminine form of put.