Согласно памятке, документы нужно подать сегодня, а вопреки моим ожиданиям очередь была короткой.

Because both are words that normally govern the dative in Russian.

• согласно памятке = according to the memo/instructions
• вопреки моим ожиданиям = contrary to my expectations

This is something you mostly have to memorize as part of each word’s pattern:

• согласно + dative
• вопреки + dative

So:

• памятка → памятке
• мои ожидания → моим ожиданиям

This is similar to how in English certain words naturally go with certain prepositions, except in Russian they often also require a specific case.

Памятке is the dative singular form of памятка.

Base form:

• памятка = a memo, instruction sheet, reminder note, guideline handout

Case form:

• nominative: памятка
• dative: памятке

So согласно памятке literally means something like in accordance with the memo/instruction sheet.

For an English speaker, памятка often feels broader than just memo. It can also mean a brief written set of instructions or guidance.

Here документы is the direct object of подать.

The structure is:

• нужно = it is necessary
• подать = to submit
• документы = documents

So literally:

• It is necessary to submit documents today

The verb подать takes the accusative case. But документы is an inanimate plural noun, and for many inanimate plural nouns, the accusative plural looks exactly like the nominative plural.

So:

• nominative plural: документы
• accusative plural: документы

That is why the form does not visibly change here.

Because the sentence uses an impersonal necessity construction:

• нужно + infinitive

So:

• нужно подать = need to submit / it is necessary to submit

There is no personal subject like I, you, or we stated here. Russian often uses this kind of impersonal structure when giving instructions or stating requirements.

Compare:

• Мне нужно подать документы = I need to submit the documents
• Документы нужно подать сегодня = The documents need to be submitted today

The second version sounds more neutral and official.

This is a question of aspect.

• подавать = imperfective
• подать = perfective

Here подать is used because the sentence refers to a single completed action: the documents must be submitted today.

So:

• нужно подать сегодня = the submission should be done today, as a completed act

If you used подавать, it would sound more like a process, repetition, or general activity, which does not fit as well here.

Very roughly:

• нужно подать документы сегодня = the documents must be submitted today
• нужно подавать документы заранее = one should submit documents in advance / as a general rule

Here нужно means need to / it is necessary to.

Yes, in many situations нужно and надо are very close in meaning:

• Документы нужно подать сегодня
• Документы надо подать сегодня

Both are natural.

A rough tendency:

• нужно can sound a little more neutral or formal
• надо can sound a little more conversational

But in many real sentences, the difference is small.

Russian word order is flexible, so сегодня could appear in different places depending on emphasis.

Here:

• документы нужно подать сегодня

This is a neutral, natural order: first the thing to be done, then the necessity, then the action, then the time.

Other orders are also possible, for example:

• Сегодня документы нужно подать
• Документы сегодня нужно подать

These may shift the emphasis slightly:

• starting with сегодня emphasizes today
• keeping сегодня at the end sounds fairly neutral and smooth

So the chosen order is natural, especially in an official or explanatory statement.

Here а marks a contrast between the two ideas:

• according to the memo, the documents must be submitted today
• contrary to my expectations, the line was short

This is not a direct logical opposition like but in every case, so а works very well.

Very roughly:

• и = and
• но = but, stronger contradiction
• а = and/but, often showing contrast or a shift to a different point

In this sentence, а helps connect two related facts while signaling a contrast in perspective or topic.

Моим ожиданиям is the dative plural of мои ожидания.

Base form:

• ожидание = expectation
• plural: ожидания = expectations

Because вопреки requires the dative, we get:

• мои ожидания → моим ожиданиям

Word by word:

• вопреки = contrary to
• моим = my
• ожиданиям = expectations

So:

• вопреки моим ожиданиям = contrary to my expectations

Russian very often uses the plural ожидания in expressions like this, just as English often says expectations.

So вопреки моим ожиданиям is the standard, idiomatic phrase.

A singular form is possible in some contexts, but here the plural sounds much more natural. It refers to your overall set of expectations, not just one isolated expectation.

So for a learner, it is best to remember:

• вопреки ожиданиям
• вопреки моим ожиданиям

as a common expression.

This is about the predicate after быть.

Russian can sometimes use either:

• nominative: очередь была короткая
• instrumental: очередь была короткой

Both are possible, but they can feel slightly different.

In many contexts, the instrumental after был / была / было / были sounds more natural when describing a state or characteristic in the situation being narrated:

• очередь была короткой = the line was short

The nominative version is also grammatical, but it may sound a bit more like simple identification or a more straightforward description.

For learners, the important thing is:

• after быть in the past or future, Russian often uses the instrumental for the predicate noun or adjective

So:

• короткая → короткой in the instrumental feminine singular

Yes, короткой is the adjective короткий in feminine instrumental singular.

And yes, короткий literally means short, but Russian also commonly uses it for things like:

• короткий разговор = a short conversation
• короткий срок = a short period
• короткая очередь = a short line / a line with few people

So in this sentence очередь была короткой means the queue was not long.

Yes. Очередь can mean:

• queue / line
• turn

But here the context clearly gives queue/line, because the sentence is about submitting documents. So:

• очередь была короткой = the line was short

If it meant turn, the surrounding context would be different.

Yes, parts of it sound fairly neutral-to-official.

Especially:

• согласно памятке
• документы нужно подать сегодня

These sound like the kind of wording you might see in instructions, administration, or public services.

The second part, вопреки моим ожиданиям очередь была короткой, sounds more like ordinary narrative or commentary, but still quite standard and polished.

So the whole sentence feels natural in written Russian, especially in an explanatory or semi-formal context.