Вечером я собираюсь поработать всего час, а потом отдохнуть.

Вечером is the instrumental case of вечер (evening).

Russian often uses the instrumental case without a preposition to express time when, especially with parts of the day:

• утром – in the morning
• днём – in/at the daytime
• вечером – in the evening
• ночью – at night

In everyday speech, вечером usually means this evening / tonight if we’re talking about today, unless context clearly points to another day.

Both can mean this evening / tonight, but there is a nuance:

• вечером – usually understood as “this evening” from context, a bit shorter and more neutral.
• сегодня вечером – literally “this evening (today)”, more explicit; you’d use it if you want to be very clear it’s about today, or to contrast with another day (e.g. вчера вечером, завтра вечером).

In your sentence, Вечером я собираюсь… will normally be understood as “This evening I’m going to…”, unless the context says otherwise.

Я собираюсь + infinitive means “I’m going to / I intend to / I plan to do X.”

Nuance:

• Я собираюсь поработать – I’m planning / intending to work (there is a decision/plan in my mind).
• Я поработаю – simple future (perfective): I will work (at some point); more like stating a future event, not focusing on the idea of a plan.
• Я буду работать – future of the imperfective: I will be working / I will work (describes a process or ongoing activity).

So я собираюсь поработать is closest to English “I’m going to work (for a bit)” or “I plan to work…”.

• собирать (non‑reflexive) = to collect, to gather (something):

  • собирать грибы – to pick mushrooms
  • собирать деньги – to collect money

• собираться (reflexive) has several meanings:

  1. to gather, to come together:
     • Мы собираемся у меня дома. – We are getting together at my place.
  2. to get ready:
     • Я собираюсь на работу. – I’m getting ready for work.
  3. to intend / to be going to (do something):
     • Я собираюсь поработать. – I’m going to work (I intend to work).

In your sentence it’s sense 3: собираться + infinitive = to intend / to be going to.

Поработать is the perfective infinitive of работать and adds two main nuances:

1. Limited time / one session – work for some time, for a while:
   • поработать час – to work for an hour (a single block of work)
2. “Do some work” / get some work done (an action with a sense of completion).

Compare:

• собираюсь работать час – I’m going to be working for an hour (focus on the process).
• собираюсь поработать час – I’m going to work for an hour / get some work done for an hour (a contained, completed work period).

In your sentence, with всего час (“only an hour”), the perfective поработать feels especially natural: it presents that hour as one small, bounded chunk of work.

Both поработать and отдохнуть are perfective and describe single, completed actions/periods:

• поработать – to do some work (for a while, one work session)
• отдохнуть – to rest (for a while, to have a rest)

With собираюсь, perfective is very common when you are planning distinct future events:

one work session → then one rest period.

You can say собираюсь работать / собираюсь отдыхать, but that usually emphasizes ongoing processes or habits rather than one bounded episode. In this specific sentence, поработать… а потом отдохнуть is the most natural choice.

Here всего means only / just and emphasizes that the amount is small:

• поработать всего час – to work only an hour / just an hour.

Synonyms:

• только час – only an hour
• лишь час – only an hour (a bit more literary or emphatic)
• всего час – only an hour, often with an emotional nuance: “just one hour, that’s not much!”

So всего adds a slight flavor of “it’s such a small amount.”

Russian often expresses duration with a bare noun in the accusative case, without a preposition:

• час – for an hour
• два часа – for two hours
• неделю – for a week
• месяц – for a month

So поработать час literally is “to work an hour”, which corresponds to English “to work for an hour”. The “for” is not translated; the accusative of duration does that job.

Yes, you can say всего один час.

Nuance:

• всего час – only an hour.
• всего один час – only one hour, with stronger emphasis on the number “one”, often to contrast with expectations (e.g. “I’ll work only one hour, not more.”)

Both are correct; всего час is a bit more neutral and shorter.

Comma: Russian normally puts a comma between two clauses that each have their own verb (even if the subject is omitted in the second clause):

• я собираюсь поработать…, а потом (я собираюсь) отдохнуть

So there are effectively two clauses joined by а, so a comma is required.

А vs. и:

• и – simple “and”, normally just adds one action to another.
• а – “and / but” with some contrast or shift; it can mean “and then / and on the other hand / whereas”.

In …поработать всего час, а потом отдохнуть, а suggests a shift from working to resting: work a bit, and then (in contrast to that) rest. It’s more natural here than и.

Russian often drops repeated words (especially the subject and the same verb) in coordinated clauses when the meaning is clear.

Full version would be:

• Вечером я собираюсь поработать всего час, а потом я собираюсь отдохнуть.

This is grammatically fine but sounds heavy and repetitive. Native speakers prefer:

• …я собираюсь поработать…, а потом отдохнуть.

Here я собираюсь is understood from context for the second action as well.

Yes, Russian word order is flexible, and both of these are possible:

• Я вечером собираюсь поработать всего час.
  • Slightly more emphasis on я вечером (it’s this evening that I’m planning it).
• Я собираюсь всего час поработать, а потом отдохнуть.
  • всего comes closer to поработать, but the meaning “only an hour” stays the same.

The original word order:

• Вечером я собираюсь поработать всего час…

sounds very natural and neutral: time → subject → plan → details. Other variants usually just shift emphasis, not change the basic meaning.