Ми чекаємо біля під’їзду, поки двері не відкриються.

Ukrainian does not have a separate grammatical form for the English present continuous. The present tense form чекаємо can mean either we wait or we are waiting, depending on context.

In this sentence, the action is clearly in progress right now, so English naturally uses are waiting.

• ми чекаємо = we wait / we are waiting

It could be omitted.

The ending -ємо in чекаємо already shows that the subject is we, so Ukrainian often leaves the pronoun out:

• Чекаємо біля під’їзду... = We’re waiting by the entrance...

Including ми can add a bit of emphasis, contrast, or clarity. So Ми чекаємо... is perfectly natural, but not strictly required.

біля means near, by, or next to.

під’їзд usually means the entrance of an apartment building, often the shared doorway/stairwell area, not just any entrance in a general sense.

So біля під’їзду means something like:

• by the building entrance
• near the entrance
• outside the apartment-block entrance

Because біля requires the genitive case.

The dictionary form is:

• під’їзд = entrance

After біля, it changes to the genitive singular:

• біля під’їзду = near the entrance

This is a very common pattern in Ukrainian:

• біля будинку = near the house
• біля машини = near the car
• біля під’їзду = near the entrance

The apostrophe shows that the ї keeps its y-like beginning and does not merge softly with the previous consonant.

So під’їзд is pronounced roughly like pid-yizd, not as if the д were softened into the next sound.

In Ukrainian spelling, this often happens after prefixes before я, ю, є, ї.

Here поки means until.

So the structure is:

• Ми чекаємо..., поки... = We are waiting..., until...

Be aware that поки can also mean while in other contexts, and by itself Поки! can mean Bye for now! But in this sentence, the meaning is clearly until.

This is one of the most common learner questions.

After поки or доки meaning until, Ukrainian very often uses не, but it does not create a normal negative meaning here.

So:

• поки двері не відкриються means until the doors open
• not until the doors do not open

This не is basically part of the standard pattern after поки in this kind of sentence.

Not necessarily. двері is a plural-only noun in Ukrainian.

That means even one physical door is normally called двері. Because the noun is grammatically plural, the verb also appears in the plural:

• двері відкриються = the door/doors will open

So even if English might say the door, Ukrainian still says двері.

відкриються is a perfective future form. It focuses on a single completed event: the moment when the doors become open.

That fits perfectly after поки meaning until, because you are waiting up to a specific result.

• відкриються = will open / will become open

If you used відкриваються, that would be a present-tense imperfective form, which would sound more like a general or repeated action, not the one future moment this sentence is talking about.

It turns the verb into the intransitive/reflexive-type form.

Compare:

• відкрити двері = to open the door
  someone opens it
• двері відкриються = the door will open
  the door itself becomes open

So відкриються is the natural way to say the doors will open without naming the person who opens them.

Because поки двері не відкриються is a subordinate clause.

Ukrainian normally separates a main clause and a subordinate clause with a comma:

• Ми чекаємо біля під’їзду, поки двері не відкриються.

This is very similar to English punctuation in sentences like:

• We wait there until the doors open.

Yes. Ukrainian word order is flexible.

The version in your sentence is neutral and natural:

• Ми чекаємо біля під’їзду, поки двері не відкриються.

But other orders are possible if you want to emphasize something:

• Біля під’їзду ми чекаємо, поки двері не відкриються.
  Emphasizes the location.

• Поки двері не відкриються, ми чекаємо біля під’їзду.
  Emphasizes the time condition first.

The meaning stays basically the same, but the focus shifts slightly.

Because here the idea of what is being waited for is expressed by the whole clause поки двері не відкриються.

So instead of saying we are waiting for X, Ukrainian says:

• Ми чекаємо..., поки...
  We are waiting until...

Also, чекати can be used without an object, just like English to wait.

If you did want to name the thing or person directly, Ukrainian often uses:

• чекати на когось / на щось in everyday speech
• or чекати когось / чогось in a more bookish or formal style

But in this sentence, the subordinate clause already gives that information.