לפני שאת חוצה את הרחוב, תעצרי ותסתכלי ימינה ושמאלה.

Because all the you forms here are feminine singular:

• את = you (said to one female)
• חוצה = crossing, feminine singular
• תעצרי = you will stop / stop, feminine singular
• תסתכלי = you will look / look, feminine singular

If you were speaking to one male, it would be:

לפני שאתה חוצה את הרחוב, תעצור ותסתכל ימינה ושמאלה.

לפני means before.

שאת is made of:

• ש־ = a linking word, often like that / when
• את = you (feminine singular)

So לפני שאת... means before you...

In natural English we might translate it simply as before you cross..., but literally it is closer to before you are crossing... or before you...

This is a very common learner question.

Hebrew often uses the present form after words like לפני ש־ in everyday speech, especially in instructions and general statements.

So:

• לפני שאת חוצה את הרחוב = before you cross the street

You can also hear:

• לפני שתחצי את הרחוב

That version uses the future and is also correct. The sentence you were given is very natural Hebrew.

Also note that חוצה agrees with את and is therefore feminine singular.

They are two completely different things.

1. In שאת, the את means you.
2. In את הרחוב, את is the direct object marker.

So:

• שאת = that/when you
• את הרחוב = marks the street as the direct object

They are spelled the same, but they do different jobs.

That את is the Hebrew direct object marker. It is used before a definite direct object.

Since הרחוב means the street and is definite because of ה־ = the, Hebrew puts את before it:

• חוצה את הרחוב = crossing the street

English has no equivalent word here, so it often feels strange to learners at first.

ה־ is the Hebrew definite article, meaning the.

• רחוב = a street
• הרחוב = the street

So את הרחוב means the street as the object of the verb.

In Modern Hebrew, the 2nd-person future is very often used as a command, especially in everyday speech.

So:

• תעצרי literally looks like you will stop
• תסתכלי literally looks like you will look

But in context they mean:

• stop
• look

This is extremely common and natural in spoken Hebrew.

Yes. Those are the true imperative forms:

• עצרי = stop! (to one female)
• הסתכלי = look! (to one female)

So this is also grammatical:

לפני שאת חוצה את הרחוב, עצרי והסתכלי ימינה ושמאלה.

In Modern Hebrew, though, many speakers prefer the future forms:

• תעצרי
• תסתכלי

They often sound more natural in everyday instructions.

They mean:

• ימינה = to the right / rightward
• שמאלה = to the left / leftward

So תסתכלי ימינה ושמאלה means look right and left or look to the right and to the left.

These are very common directional words.

That final ־ה is an old directional ending sometimes called the directional he.

It adds the idea of toward or in the direction of.

So:

• ימין = right

• ימינה = to the right

• שמאל = left
• שמאלה = to the left

In modern Hebrew, learners usually just memorize these as common adverb-like direction words.

Yes. Both are possible.

• ימינה ושמאלה
• לימין ולשמאל

Both mean to the right and to the left.

In this kind of safety instruction, ימינה ושמאלה sounds especially natural and idiomatic.

The basic infinitives are:

• לחצות = to cross
• לעצור = to stop
• להסתכל = to look

So the sentence uses forms of these three verbs:

• חוצה from לחצות
• תעצרי from לעצור
• תסתכלי from להסתכל

Yes. לחצות is the standard verb for to cross, especially for crossing from one side to another, such as a street or border.

So:

• לחצות את הרחוב = to cross the street

That is the most natural and standard wording here.