Когда всё было готово, мы разложили еду на пледе и открыли термос с чаем.

Because Когда всё было готово is a subordinate time clause: When everything was ready. In Russian, subordinate clauses are normally separated from the main clause with a comma.

So the structure is:

Когда всё было готово,
мы разложили еду на пледе и открыли термос с чаем.

This is very standard Russian punctuation.

Because всё means everything, and grammatically it is treated as singular neuter in Russian.

So the words agreeing with it are also singular neuter:

• всё — neuter singular
• было — past tense neuter singular of быть
• готово — neuter singular short-form adjective

Были готовы would be plural, so it would not match всё.

Here готово is a short-form adjective used as part of the predicate, meaning ready in the sense of a state.

Russian often uses the short form after быть or when describing a condition:

• Всё готово. — Everything is ready.
• Ужин готов. — Dinner is ready.
• Дверь закрыта. — The door is closed.

The full form готовое would usually describe a noun directly, like готовое блюдо meaning a ready-made dish. It would not sound right in всё было готово.

Here когда means when, introducing the moment or situation after which the main action happened.

So the sense is:

When everything was ready, we laid out the food...

It is not really while here. While would suggest an action happening at the same time as another ongoing action, but this sentence describes a completed state first, then the next actions.

Разложили is perfective, which means the action is viewed as completed: they finished laying out the food.

That fits the context well: at a picnic, they got everything ready, then they laid out the food, then opened the thermos. These are complete, one-time actions.

If you used раскладывали, that would be imperfective, focusing more on the process:

• Мы раскладывали еду... — We were laying out the food / used to lay out the food

In this sentence, the completed action is more natural, so разложили is the expected choice.

In this context, разложили еду means something like:

• laid out the food
• spread out the food
• arranged the food

It is a very natural choice for a picnic scene. It suggests putting the food out on the blanket so it is ready to eat.

It does not necessarily mean each item was carefully arranged; it just means the food was taken out and placed out for the meal.

Because еду is the accusative case of еда.

Here еда is the direct object of разложили:

• разложили что? — laid out what?
• еду — food

So:

• nominative: еда
• accusative: еду

This is a very common pattern in Russian: the direct object often goes into the accusative.

Because here на means on in the sense of location, not movement toward a destination.

Russian distinguishes these two ideas:

• на + accusative = motion onto something
• на + prepositional = location on something

So:

• положили еду на плед — put the food onto the blanket
• еда лежала на пледе — the food was lying on the blanket
• разложили еду на пледе — laid out the food on the blanket

In your sentence, the focus is on where the food ended up being laid out, so на пледе is natural.

Because after на in the meaning of location, Russian uses the prepositional case.

The noun плед is masculine, and its prepositional singular form is пледе:

• nominative: плед
• prepositional: на пледе

So на пледе means on the blanket.

Yes, с literally means with, but in Russian it is also often used in phrases like this to describe what something contains or comes with.

So термос с чаем means:

• a thermos with tea
• more naturally in English: a thermos of tea

Russian often uses с + instrumental in this way:

• чашка с кофе — a cup of coffee
• бутерброд с сыром — a sandwich with cheese
• пирог с яблоками — an apple pie

So this is a very normal Russian construction.

Because the preposition с normally requires the instrumental case.

The noun чай changes like this:

• nominative: чай
• instrumental: чаем

So:

• с чаем — with tea

That is why you get термос с чаем.

Because both verbs have the same subject: мы.

Russian, like English, does not need to repeat the subject when two actions are connected:

• мы разложили еду на пледе и открыли термос с чаем

This means:

• we laid out the food on the blanket and opened the thermos of tea

Repeating мы would be possible in some contexts for emphasis, but it is not necessary here.

Yes. Russian word order is flexible, although some orders sound more natural than others depending on emphasis.

The original sentence is neutral and natural:

Когда всё было готово, мы разложили еду на пледе и открыли термос с чаем.

You could also say:

Мы разложили еду на пледе и открыли термос с чаем, когда всё было готово.

But that version sounds a little different in focus. The original puts the time/background first, which is very common in storytelling.

So the word order is not random; it helps show what information is background and what is the main event.

Russian does not have a direct tense system matching all English forms like had been ready. Instead, it usually relies on context, aspect, and sentence structure.

In this sentence:

• Когда всё было готово — when everything was ready
• мы разложили... и открыли... — we laid out... and opened...

The sequence of events is clear from the meaning, so Russian does not need a special pluperfect form.

This is very common: Russian often uses simple past forms where English might choose had done, had been, or simple past depending on style.