من عادتنا أن نجلب العصير ونلتقي في الحديقة العامة.

It means it is our habit or it is our custom.

Literally, من عادتنا is something like from our habit or among our habits, but in natural English you usually translate it as:

• It is our habit to...
• We usually...
• It is our custom to...

So the sentence is presenting a regular, customary action.

Yes, من often means from, but here it is part of an idiomatic expression.

In من عادتنا أن..., the idea is:

• من = from / among
• عادتنا = our habit

So the phrase suggests this is something that belongs to our habits/customs.

A very natural English equivalent is simply:

• It is our habit to...
• One of our habits is to...

So you should learn من عادتنا أن... as a useful set expression.

Both are possible, but they are slightly different in nuance.

• من عادتنا أن... = It is our habit to...
  This is very common and idiomatic.
• من عاداتنا أن... = Among our habits/customs is that...
  This sounds a bit more like you are referring to your customs in general.

In many contexts, من عادتنا is the more natural fixed expression for we usually do this.

أن introduces a verb phrase meaning to do something.

So:

• أن نجلب = to bring
• أن نلتقي = to meet

After أن, the present-tense verb is in the subjunctive in formal grammar.

So the structure is:

• من عادتنا أن نجلب العصير
  = It is our habit to bring juice

This is a very common pattern in Arabic.

It applies to both verbs.

So:

• أن نجلب العصير ونلتقي في الحديقة العامة

means:

• to bring juice and meet in the public park

The second verb نلتقي is coordinated with the first by و and is understood as still being under أن.

So grammatically the meaning is:

• أن نجلب العصير وأن نلتقي في الحديقة العامة

But Arabic often does not repeat أن when it is already understood.

Both are first person plural present verbs:

• نجلب = we bring
• نلتقي = we meet

In this sentence, because they come after أن, they are best understood in English as infinitives:

• to bring
• to meet

But the actual Arabic verb form is still the present tense form, not a separate infinitive form. Arabic does not have an infinitive in the same way English does.

Because the verb itself already tells you the subject.

In Arabic, the prefix نـ at the start of the verb usually marks we:

• نجلب = we bring
• نلتقي = we meet

So نحن is not necessary unless you want extra emphasis.

If you said نحن نجلب, that would be more like we are the ones who bring or we bring with emphasis.

Yes, العصير literally means the juice, because of الـ.

But in Arabic, a definite noun can sometimes be used more generally than in English. Depending on context, العصير could mean:

• the juice specifically
• juice in a general sense
• the juice we usually bring

So even if English translation simply says juice, Arabic may naturally use العصير.

If you wanted an indefinite sense, you could also say عصيرًا, but العصير is perfectly natural here.

نلتقي means we meet or we get together.

In this sentence, it does not name a separate object, so the meaning is something like:

• we meet up
• we get together

The location is given by:

• في الحديقة العامة = in the public park

So the idea is not necessarily we meet someone else, but rather we meet there / we gather there.

Because in Arabic, prepositions come before the noun phrase, just as in English:

• في الحديقة العامة = in the public park

So the order is:

• في = in
• الحديقة = the garden / park
• العامة = public

Arabic adjective phrases normally come:

1. noun first
2. adjective after it

So الحديقة العامة literally looks like the park public, but in English we say the public park.

Because العامة is an adjective describing الحديقة.

In Arabic, adjectives usually come after the noun and must agree with it in:

• definiteness
• gender
• number
• case

Here:

• الحديقة is feminine singular definite
• so the adjective must also be feminine singular definite
• therefore: العامة

So:

• حديقة عامة = a public park
• الحديقة العامة = the public park

Yes, literally حديقة often means garden, but in many contexts it is also used for park.

So:

• الحديقة العامة very naturally means the public park

This is a good example of where the most natural English translation is not always the most literal word-for-word one.

A fully vowelled version would be:

مِنْ عادَتِنا أَنْ نَجْلِبَ العَصيرَ وَنَلْتَقِيَ في الحَديقَةِ العامَّةِ

The endings show the grammar:

• عادتِنا is genitive after من
• نجلبَ is subjunctive after أن
• العصيرَ is the direct object
• الحديقةِ is genitive after في
• العامةِ matches الحديقةِ as its adjective

In normal Arabic writing, these short vowels are usually not written, so learners have to get used to recognizing the grammar from context.

Yes, it is natural and correct in MSA.

It sounds like a clear, slightly formal sentence meaning that this is a regular custom or habit. A native speaker might also express the same idea in other ways, for example:

• اعتدنا أن نجلب العصير ونلتقي في الحديقة العامة
• من المعتاد عندنا أن نجلب العصير ونلتقي في الحديقة العامة

But your original sentence is perfectly good Modern Standard Arabic.