تأكدي من العنوان قبل ما تبعتي الدعوة، لانه كتبناه غلط قبل.

Because the sentence is addressed to one woman.

In Levantine Arabic, verbs for you change depending on gender and number:

• to a woman: تأكدي ... تبعتي
• to a man: تأكد ... تبعت
• to a group: تأكدوا ... تبعتوا

So the -ي ending here tells you the speaker is talking to a female singular addressee.

The verb is تأكّد من, which means to make sure of, to check, or to verify something.

So:

• تأكدي من العنوان = make sure of the address / check the address

The من is not random; it belongs with the verb. English says make sure of or just check, but Arabic often keeps that من after تأكّد.

After قبل ما in Levantine, you very often use the bare imperfect (without بـ) for a future or one-time action.

So:

• قبل ما تبعتي = before you send
• not usually قبل ما بتبعتي in this kind of sentence

A simple way to think about it is:

• بـ often goes with present/habitual meaning
• after قبل ما, the verb often appears without بـ because it refers to something that has not happened yet

Because يبعت / بعث is a very common everyday Levantine verb meaning to send.

So:

• تبعتي الدعوة = you send the invitation

You may also learn يرسل from Standard Arabic, but يبعت sounds much more natural in everyday spoken Levantine.

لانه means because here.

It corresponds to Standard Arabic لأنه, but in casual Levantine writing people often write it without the hamza: لانه.

It is commonly pronounced something like laʾanno or la2anno.

So:

• لانه كتبناه غلط قبل = because we wrote it wrong earlier / before

كتبناه = كتبنا + ه

• كتبنا = we wrote
• ـه = it

So كتبناه means we wrote it.

Here, it refers to العنوان (the address), which is grammatically masculine in Arabic, so the pronoun is ـه.

In spoken Arabic, غلط often works like wrong or wrongly/incorrectly, depending on context.

So:

• كتبناه غلط literally = we wrote it wrong
• natural English = we wrote it incorrectly

This is very normal colloquial Arabic. Arabic often uses words like غلط in a way that feels adjective-like in form but adverb-like in meaning.

Because it is doing two different jobs:

• قبل ما تبعتي = before you send
• قبل at the end = before / earlier / previously

So the first قبل introduces another action, while the second one means earlier in time.

A natural English understanding is:

• Make sure of the address before you send the invitation, because we wrote it wrong earlier.

Arabic often uses the when the thing is already known from context.

So الدعوة probably means a specific invitation that both speakers already know about. English sometimes uses the too, but sometimes English would sound more natural with no article or with an, depending on context.

This is a very common difference between Arabic and English: Arabic often makes nouns definite when the situation is already clear to the people speaking.