חוץ מההערה האחרונה שלך, אני מסכים עם כל מה שכתבת.

חוץ מ־ means except for, apart from, or other than.

So חוץ מההערה האחרונה שלך means apart from your last comment or except for your last comment.

A very literal sense is something like outside of, but in normal English you usually translate it as except for or apart from.

Because חוץ normally takes the preposition מ־ after it.

So the structure is:

חוץ מ־ + ההערה

When מ־ attaches to the next word, you get:

מההערה

That is completely normal. The two ה letters are not a mistake:

• the first ה is the definite article the
• the second ה is the first letter of הערה

So מההערה simply means from / except for the remark after חוץ.

Because in Hebrew, adjectives usually come after the noun.

So:

• הערה אחרונה = a last remark
• ההערה האחרונה = the last remark

Also, the adjective must match the noun in:

• gender
• number
• definiteness

Here הערה is feminine singular and definite, so the adjective is also feminine singular and definite: האחרונה.

That is a very common Hebrew word order for a noun phrase with both an adjective and a possessive pronoun:

noun + adjective + שלך

So:

• ההערה האחרונה שלך = your last remark

This is more natural than trying to place שלך earlier.

English puts your first, but Hebrew often puts the possessive pronoun after the noun phrase.

Yes, Hebrew can sometimes omit the subject pronoun, so מסכים עם כל מה שכתבת can work in context.

But אני מסכים is very natural because in the present tense Hebrew uses a participle-like form, and the pronoun often helps make the subject explicit.

Also, מסכים tells you the speaker is masculine singular.

If the speaker were female, it would be:

אני מסכימה

Because the verb להסכים commonly goes with עם when you mean agree with someone or with something.

So:

• אני מסכים עם זה = I agree with that
• אני מסכים עם כל מה שכתבת = I agree with everything you wrote

Hebrew also uses other patterns with להסכים, for example:

• להסכים ל־ = to agree to
• להסכים ש־ = to agree that

But here the meaning is agree with, so עם is the natural choice.

Literally, it is something like:

all what that-you-wrote

But in natural English it means:

everything that you wrote
or
all that you wrote

This is a very common Hebrew structure:

כל מה ש־...

It means everything that... or all that...

The ש־ is a very common Hebrew connector meaning that, which, or who, depending on context.

Here it links מה to the clause כתבת:

• מה שכתבת = what you wrote
• more literally, that which you wrote

So in כל מה שכתבת, the ש־ is what turns the phrase into everything that you wrote.

Because the speaker is referring to something the other person has already written.

So כתבת means you wrote.

That matches the English idea of everything you wrote.

Hebrew often uses the simple past here, just as English does.

Not in normal unpointed spelling.

Without vowel marks, כתבת can mean:

• you wrote to a man
• you wrote to a woman

The masculine and feminine singular forms are spelled the same without ניקוד.

Also, שלך is the same for both masculine and feminine singular you.

So this sentence is clearly addressed to one person, but their gender is not shown in ordinary spelling.

Putting חוץ מההערה האחרונה שלך at the beginning gives it emphasis. It sets up the exception first:

Apart from your last comment, ...

The comma helps mark that introductory phrase.

You could also say:

אני מסכים עם כל מה שכתבת, חוץ מההערה האחרונה שלך.

That version is also natural, but it puts the main agreement first and the exception afterward. The original sentence highlights the exception right away.