Learn Hardcore Russian: Мне нужно подойти к кассе и сохранить чек. - I need to go up to the cash desk and keep the receipt.

Russian often expresses “I need…” using the structure кому (dative) + нужно + infinitive.
So Мне нужно подойти… literally means “To me it is necessary to approach…,” i.e. “I need to go…” / “I have to…”

What exactly does нужно mean here, and can it change?

Нужно means “it is necessary / one must / need to.” It’s an impersonal predicate word, so it doesn’t agree with мне.
You can swap it for similar words:

Мне надо… = more colloquial “I need to…”
Мне необходимо… = more formal “It is necessary for me to…”

Why is подойти perfective, and what would подходить change?

Подойти (perfective) focuses on a single completed action: “go up to / approach (and arrive).”
If you used подходить (imperfective), it would sound more like a general process/habit or background action, e.g. “I need to be approaching / to come up (in general).” In this “do this once” instruction context, perfective подойти is natural.

What is the difference between подойти к кассе and подойти на кассу?

Подойти к кассе = “go up to the cash register / cashier area” (approach it). This is the standard phrasing.
На кассу is used in some contexts to mean “to the checkout” (especially “go to the checkout line/area”), but подойти к кассе is safer and more universally correct.

Why is кассе in the form кассе and not касса?

Because к (“to/toward”) requires the dative case.
касса (nom.) → к кассе (dat.).
Same pattern: к двери, к врачу, к метро (though метро doesn’t change).

What does касса refer to: the machine or the person?

Касса can mean:

the cash register / checkout counter,
the cashier station,
sometimes the cashier’s desk/area as a whole.
In everyday situations, к кассе is understood as “to the checkout/cashier.”

Why is и used, and does it imply order (“first…, then…” )?

И simply joins two required actions: подойти… и сохранить… = “go up… and keep/save…”
It often implies a natural sequence (you approach the checkout, and then you keep the receipt), but grammatically it’s just “and.” If you want to emphasize “then,” you might add потом (“then”).

What does сохранить чек mean—keep it physically, or “save” it digitally?

In most real-life contexts it means “keep/retain the receipt” (don’t throw it away).
It can also mean “save” in the sense of “store” (e.g., for returns, warranty, reporting). If the context is an app/e-receipt, it could mean “save it,” but default is “keep the paper receipt.”

Why is сохранить perfective, and what would сохранять mean?

Сохранить (perfective) = “to keep/save (successfully),” a one-time result: “make sure you end up with it kept.”
Сохранять (imperfective) = “to be keeping/saving” as a process or repeated action, e.g. “I always keep receipts” → Я сохраняю чеки.

Is чек accusative here, and why doesn’t it look different?

Yes: сохранить takes a direct object in the accusative.
For inanimate masculine nouns like чек, the accusative singular is the same as the nominative singular: чек.

Could it be сохранить чек or сохранить чекy? How do I know which case to use?

It’s сохранить чек (accusative) because сохранить is a transitive verb meaning “to keep/save [something].”
Dative (чеку) would be used with verbs like помочь (“help”) or дать (“give”), not with “keep.”

Is there any difference between чек and квитанция?

Often:

чек = receipt from a shop/cash register (common in retail).
квитанция = receipt/statement, often for payments, utilities, official fees, or a more “document-like” proof.
In a store checkout context, чек is the expected word.

Can I say Мне нужно подойти к кассиру instead of к кассе?

Yes, but it slightly shifts focus:

к кассе = to the checkout/register area (standard).
к кассиру = to the cashier (the person).
Both can work; к кассе is more typical in a “go to checkout” instruction.

Is the sentence formal or informal?

It’s neutral and natural—appropriate in most everyday situations.
For a more colloquial tone you might hear Мне надо подойти к кассе и сохранить чек.
For a more formal tone: Мне необходимо подойти к кассе и сохранить чек.