После ужина я убрала салат в контейнер и поставила его в холодильник.

Because после normally requires the genitive case.

• ужин = dinner/supper
• ужина = genitive singular of ужин

So:

• после ужина = after dinner

This is a very common pattern in Russian:

• после работы = after work
• после урока = after the lesson
• после фильма = after the movie

Russian past tense verbs agree with the subject in gender and number.

Here the subject is я, and the speaker is understood to be female, so:

• я убрала = I put away / I put
• я поставила = I placed / I put

If the speaker were male, it would be:

• я убрал
• я поставил

If it were plural:

• мы убрали
• мы поставили

This is something English does not do, so it often stands out to learners.

Good question: убрать has a broader meaning than a single English verb.

In this sentence, убрала салат в контейнер means something like:

• put the salad away into a container
• transferred the salad into a container
• stored the salad in a container

Depending on context, убрать can mean:

• to remove
• to tidy away
• to clear away
• to put away

So here it is not really cleaned the salad. It is the idea of putting it away/storing it.

Because Russian uses different cases depending on whether there is movement into a place or location in a place.

Here there is movement into the container, so Russian uses:

• в + accusative
• в контейнер

Compare:

• Я убрала салат в контейнер. = I put the salad into a container.
• Салат в контейнере. = The salad is in the container.

So:

• в контейнер = into the container
• в контейнере = in the container

This is a very important Russian pattern.

For the same reason: this sentence describes motion into the fridge, not location inside it.

So Russian uses:

• в холодильник = into the fridge

If you wanted to say that something is already there, you would use:

• в холодильнике = in the fridge

Compare:

• Я поставила его в холодильник. = I put it into the fridge.
• Он стоит в холодильнике. = It is sitting in the fridge.

Russian often chooses different verbs depending on the kind of placing involved.

поставить literally means to place / set / stand something somewhere, often implying that you put an object down in a stable position.

So:

• поставить контейнер в холодильник sounds natural
• you are placing the container into the fridge

Russian often distinguishes verbs like:

• положить = to lay/put something down
• поставить = to set/stand something
• повесить = to hang something

English often just says put, but Russian is more specific.

Grammatically, его could in principle refer to either one, because both салат and контейнер are masculine singular nouns.

But in normal interpretation, его most naturally refers to контейнер.

Why?

Because the sequence is:

1. убрала салат в контейнер = put the salad into a container
2. поставила его в холодильник = put it into the fridge

What usually goes into the fridge in that situation is the container with the salad in it.

So English would naturally understand this as:

• I put the salad into a container and put it in the fridge

where it = the container.

Yes, Russian often can omit the subject pronoun, because the verb ending already shows the person.

So these are both possible:

• После ужина я убрала салат в контейнер...
• После ужина убрала салат в контейнер...

Including я can make the sentence:

• clearer
• slightly more explicit
• more natural in some contexts
• a bit more contrastive if needed

In English, you usually must say I, but in Russian it is optional much more often.

Here салат is the direct object of убрала, and because it is an inanimate masculine noun, the accusative singular looks the same as the nominative singular.

So:

• nominative: салат
• accusative: салат

That is why there is no visible change.

Compare that with a feminine noun like тарелка:

• nominative: тарелка
• accusative: тарелку

And with animate masculine nouns, the accusative often looks different too.

Both are perfective:

• убрать → убрала
• поставить → поставила

Perfective verbs present the actions as completed whole events.

That fits this sentence well, because the speaker is describing completed actions:

• she finished putting the salad into a container
• she finished putting it into the fridge

If you used imperfective forms, the meaning would shift toward process, repetition, background description, or habitual action.

Very roughly:

• убрала / поставила = did it, completed it
• убирала / ставила = was putting away / used to put / was in the process of placing

Because the sentence describes two different stages of the action.

1. убрала салат в контейнер
   She put the salad away into a container.

2. поставила его в холодильник
   She placed the container in the fridge.

Using two verbs makes the sequence more natural and specific. Russian often prefers this kind of precision where English might simply say put ... and put ....

Yes, контейнер is a normal Russian word, and yes, it is a borrowing.

In everyday speech, контейнер is commonly used for a food container, storage container, or similar object.

Depending on context, Russian speakers might also say things like:

• судок in some regions
• ёмкость
• банка
• коробка

But контейнер is completely standard and natural here.

Russian word order is flexible, but the given order is very natural.

После ужина я убрала салат в контейнер и поставила его в холодильник.

This order works well because it presents the information in a clear sequence:

1. time: После ужина
2. subject: я
3. action 1: убрала салат в контейнер
4. action 2: и поставила его в холодильник

You could rearrange parts for emphasis, but the meaning or focus might shift. For example, moving после ужина later would sound different stylistically, and moving его or в холодильник could emphasize the fridge or the object.

So the word order is not the only possible one, but it is a very standard, neutral one.