Погрузка закончится сегодня, разве что грузовой лифт не заработает.

Here разве что means something like unless, except if, or the only exception would be if.

So the sentence is saying that the loading will finish today, with one possible exception: if the freight elevator does not start working.

This expression is common in conversational Russian and often introduces a limiting condition or exception.

Examples:

• Я приду, разве что будет сильный дождь.
  I’ll come, unless it rains heavily.
• Успеем, разве что пробки будут ужасные.
  We’ll make it, unless the traffic is terrible.

No, it is not a double negative.

The negation belongs only to the verb заработает:

• заработает = will start working / will begin functioning
• не заработает = will not start working / will fail to work

So:

• разве что грузовой лифт не заработает = unless the freight elevator doesn’t start working

This can feel slightly awkward to an English speaker because English unless ... not can sound logically confusing. But in Russian this structure is normal.

Compare:

• разве что лифт не заработает = unless the elevator doesn’t start working
• разве что лифт заработает would mean something quite different, more like except perhaps if the elevator starts working

So the не is important and directly changes the meaning.

Закончится is the 3rd person singular future form of закончиться.

Breakdown:

• закончиться = to finish / to come to an end
• закончится = it will finish / it will end

The subject is погрузка (the loading process), which is feminine singular, but in the future tense this verb form is the same for masculine, feminine, and neuter singular in the 3rd person:

• он закончится
• она закончится
• оно закончится

It is used here because the sentence talks about a completed future event: the loading will be finished today.

Because Russian is using the perfective aspect here.

• закончиться is perfective: it focuses on the result or completion.
• заканчиваться is imperfective: it focuses on the process or repeated action.

In this sentence, the speaker means that the loading will reach completion today, so perfective закончится is the natural choice.

Compare:

• Погрузка закончится сегодня.
  The loading will finish today.
• Погрузка будет заканчиваться сегодня вечером.
  The loading will be winding down this evening.
  This sounds more process-focused and less direct.

So закончится is best because the important idea is the completed end point.

Yes, работать means to work / to function. But заработать is a perfective verb that often means to begin to work, especially for machines, systems, devices, or services.

So:

• лифт работает = the elevator is working
• лифт заработал = the elevator started working / came on / began functioning
• лифт не заработает = the elevator won’t start working

This is very common in Russian:

• Компьютер заработал. = The computer started working.
• Интернет наконец заработал. = The internet finally started working.

So in this sentence, the idea is not that the elevator is actively doing labor, but that it becomes operational.

Погрузка is a noun meaning loading or the loading process.

It comes from the verb погрузить / погружать = to load.

In this sentence, погрузка refers to the operation of loading goods, cargo, furniture, etc.

This kind of noun is very common in Russian:

• погрузка = loading
• разгрузка = unloading
• поставка = delivery/supply
• проверка = inspection/check

Russian often uses such nouns where English might also use a verbal phrase:

• Погрузка закончится сегодня
  literally: The loading will finish today more naturally in English: Loading will be finished today

Because the sentence contains two clauses:

1. Погрузка закончится сегодня
2. разве что грузовой лифт не заработает

The second clause gives an exception or condition to the first, so Russian separates it with a comma.

This is very typical when разве что introduces a clause:

• Поедем завтра, разве что погода испортится.
• Он согласится, разве что цена окажется слишком высокой.

So the comma helps show that the second part modifies the first part as an exception.

Because it is the subject of the clause грузовой лифт не заработает.

• лифт = elevator/lift
• грузовой лифт = freight elevator / service elevator / cargo lift

Since the elevator is the thing that may or may not start working, it stands in the nominative case.

Also notice the adjective agreement:

• лифт is masculine singular
• so the adjective is грузовой (masculine singular nominative)

If the noun changed, the adjective would change too:

• грузовая машина = cargo vehicle
• грузовое отделение = cargo compartment

Грузовой means cargo, freight, or for carrying goods.

It comes from груз = cargo / load / freight.

So:

• грузовой лифт = freight elevator
• грузовой поезд = freight train
• грузовая машина = cargo truck / truck

It contrasts with things meant for people:

• пассажирский лифт = passenger elevator
• грузовой лифт = freight elevator

So this sentence specifically refers to the elevator used for moving goods, not people.

Yes, Russian word order is flexible, but the original order is the most neutral and natural.

Original:

• Погрузка закончится сегодня, разве что грузовой лифт не заработает.

You could also hear:

• Разве что грузовой лифт не заработает, погрузка закончится сегодня.

But that version sounds more marked or stylistic, because it starts with the exception.

Russian often changes word order to shift emphasis, but in ordinary neutral statements, the original order is preferred:

1. main statement first
2. exception second

The -ся marks the verb as reflexive, but in many verbs like this it does not mean literal self-action. Instead, it forms a verb with a slightly different meaning.

Compare:

• закончить что-то = to finish something
• закончиться = to finish / to come to an end

So:

• Они закончат погрузку сегодня.
  They will finish the loading today.
• Погрузка закончится сегодня.
  The loading will finish today / will be finished today.

This is a very common pattern in Russian:

• открыть дверь = to open the door
• дверь открылась = the door opened

So -ся often helps make a verb intransitive: the event happens to the subject, rather than the subject acting on an object.

Yes, сегодня is being used as a time adverb meaning today.

Russian often uses time words without prepositions:

• сегодня = today
• завтра = tomorrow
• вчера = yesterday

So:

• Погрузка закончится сегодня = The loading will finish today

If you want to be more specific, Russian may use a preposition:

• сегодня вечером = this evening / tonight
• к сегодняшнему вечеру = by this evening
• в течение сегодняшнего дня = during today

But in this sentence, plain сегодня is enough and perfectly natural.