אם ההצעה הזאת לא טובה, נחפש אפשרות אחרת.

Here אם means if and introduces a condition:

• אם ההצעה הזאת לא טובה = if this proposal/suggestion is not good
• נחפש אפשרות אחרת = we will look for another option

So the whole sentence is a standard if ... then ... type of sentence, even though Hebrew does not need a separate word for then here.

Because Hebrew usually makes the noun definite when it is followed by this/that.

• הצעה = a proposal / proposal
• ההצעה הזאת = this proposal

So in normal Hebrew, this proposal is expressed with:

• the definite article ה־ on the noun
• plus the demonstrative הזאת

This is different from English, where this already makes the noun definite by itself.

Yes, both are related forms meaning this for a feminine singular noun.

Here:

• הצעה is feminine singular
• so the demonstrative must also be feminine singular

Common options are:

• ההצעה הזאת = very common everyday wording
• הצעה זו = more formal/written style
• ההצעה הזו = also very common in modern spoken Hebrew

So הזאת is correct and natural here, especially in everyday speech.

Because it describes הצעה, and הצעה is a feminine singular noun.

In Hebrew, adjectives usually agree with the noun in:

• gender
• number
• definiteness in some contexts

So:

• טוב = masculine singular
• טובה = feminine singular

Since הצעה is feminine singular, you say:

• ההצעה הזאת לא טובה = this proposal is not good

In Hebrew, the verb to be is usually omitted in the present tense.

So English:

• this proposal is not good

becomes Hebrew:

• ההצעה הזאת לא טובה

Literally, it looks like:

• this proposal not good

This is completely normal Hebrew.
If the sentence were in the past or future, Hebrew would use forms of to be more explicitly when needed.

לא is the normal Hebrew word for not, and it usually comes directly before what it negates.

So:

• טובה = good
• לא טובה = not good

That is the standard way to negate an adjective or predicate in a sentence like this.

נחפש means we will look for or we will search for.

It comes from the verb לחפש = to look for / to search for.

The form נחפש is:

• future tense
• first person plural
• we will ...

So:

• נחפש אפשרות אחרת = we will look for another option

It is built into the verb.

In Hebrew, verbs often already show the subject, so you do not need a separate pronoun unless you want emphasis or contrast.

• נחפש = we will look for
• אנחנו נחפש = we will look for / we will look for

The second version is more emphatic. In your sentence, the plain verb is enough.

Because אפשרות is a feminine singular noun, and אחרת must agree with it.

So:

• אחר = masculine singular
• אחרת = feminine singular

Therefore:

• אפשרות אחרת = another option

This is the same kind of agreement you saw in טובה with הצעה.

Because it is indefinite here.

• אפשרות אחרת = another option
• האפשרות האחרת = the other option

Your sentence means we’ll look for another option, not the other option, so the indefinite form is the correct one.

Yes, this word order is very normal:

• אם
  • condition
• main clause in the future

So:

• אם ההצעה הזאת לא טובה, נחפש אפשרות אחרת.

This is a very natural way to say it.

You might also hear close variants, such as:

• אם ההצעה הזו לא טובה, נחפש אפשרות אחרת.
• אם ההצעה הזאת לא טובה, אנחנו נחפש אפשרות אחרת.

The version you have is straightforward and idiomatic.

The comma separates the conditional clause from the main clause.

• אם ההצעה הזאת לא טובה = the condition
• נחפש אפשרות אחרת = the result

This is similar to English writing:

• If this proposal isn’t good, we’ll look for another option.

So the comma helps show the structure clearly.

A simple pronunciation guide is:

im ha-hatsa'ah ha-zot lo tovah, nekhapes efsharut akheret

A few notes:

• אם = im
• ההצעה is roughly ha-hatsa'ah
• זאת here is roughly ha-zot
• נחפש is roughly nekhapes
• אפשרות is roughly efsharut
• אחרת is roughly akheret

Pronunciations vary a bit by speaker and accent, but this will guide an English speaker fairly well.