hěnduō tóngxué xiàkè yǐhòu qù jùhuì, kěshì wǒ xiǎng huíjiā xiūxi.

很多 means “many / a lot of” and is used before a noun to show a large quantity:

• 很多同学 = many classmates

很 by itself usually means “very” and is used before adjectives, not nouns:

• 很高 = very tall
• 很忙 = very busy

You cannot say 很同学 to mean “many classmates”; that’s ungrammatical. You need 很多同学 or just 同学们 (the classmates).

同学 literally means “person who studies together with you”, so its most direct meaning is “classmate / schoolmate.”

But in daily speech, when students talk to each other, 同学 can also be used like “student” in some contexts, especially in addresses:

• 老师对同学说：… = The teacher says to the students: …

Chinese usually does not mark plural on nouns if the context already makes it clear.

• 很多同学 already tells you there are many people, so adding 们 is unnecessary.
• You could say 很多同学们, but it sounds redundant and is usually avoided.
• 同学们 (without 很多) is common when addressing a group:
  
  • 同学们，好！= Hello, students / classmates!

下课 literally means “to finish class / class ends.”

It functions like a verb phrase:

• 我们三点下课。= We finish class at three.
• 老师还没下课。= The teacher hasn’t ended the class yet.

In your sentence, 下课以后 means “after (we) finish class / after class (ends)”. It’s “verb + 以后” making a time phrase, roughly “after finishing class.”

以后 (after) normally comes after the thing/event it refers to:

• 下课以后 = after class ends
• 吃完饭以后 = after finishing eating
• 工作以后 = after work

以后下课 would sound like “later then have class end,” which is not the intended structure here. The normal pattern is:

[Event] + 以后 + [What happens then]
下课以后 + 去聚会 = After class ends, (they) go to a party.

Yes, you can say 下课了以后, and it’s also correct.

• 下课以后 feels neutral and can describe habitual actions (“After class, we (usually) …”) or a specific time, depending on context.
• 下课了以后 emphasizes that the action “class ends” is completed; it often feels a bit more like a specific occasion.

In many everyday situations, people just say 下课以后 and the meaning is clear.

去 means “to go (to)” and 聚会 can be a noun (“a gathering/party”) or a verb (“to get together, to party”).

• 去聚会 is like “go (and) attend a gathering” / “go to a party.”

If you say 下课以后聚会, then 聚会 is read more like a verb: “After class, (they) get together / have a gathering.”

Both are grammatical, but:

• 下课以后去聚会 emphasizes the motion (“go somewhere to party”).
• 下课以后聚会 emphasizes the activity itself.

In spoken Chinese, 去 + (activity) is very common for saying “go do X”:

• 去吃饭 = go eat
• 去看电影 = go watch a movie
• 去玩 = go have fun

聚会 can be both:

• Noun: a gathering, a party, a get-together
  
  • 我们周末有一个聚会。= We have a party this weekend.
• Verb: to gather, to have a get-together
  
  • 周末我们聚会。= We get together on the weekend.

In 去聚会, it’s easiest to understand it as “go (attend) a gathering”. Grammatically it behaves like a verb phrase “go to have a gathering.”

All three can mean “but / however”, and they often can replace each other.

Typical feel (not strict rules):

• 但是 – very common, slightly formal / neutral, works in writing and speech.
• 可是 – very common in spoken Chinese, can sound a bit more emotional or conversational.
• 不过 – often means “however / but (not that big a contrast)”, feels softer.

Your sentence is conversational and contrasts what many classmates do with what I want to do, so 可是 fits the spoken tone well:

很多同学下课以后去聚会，可是我想回家休息。
Many classmates go to a party after class, but I want to go home and rest.

Both 想 and 要 can be translated as “want,” but they feel different:

• 想 + verb = feel like, would like to, intend to
  
  • 我想回家休息。= I’d like to go home and rest / I feel like going home to rest.
• 要 + verb = want to (more determined), going to (stronger intention or plan)
  
  • 我今天要回家休息。= I’m going to go home and rest today (plan/decision).

In your sentence, 想 sounds more polite, gentle, and subjective — it’s about what the speaker feels like doing, in contrast to what others are doing. Using 要 would sound more like a firm decision: “I will go home and rest.”

Both are correct, but they’re used a bit differently:

• 回家 = go back home / return home
  
  • Directional verb: 回 + 家
  • Very common, simple, neutral.
• 回到家 = return to home, with 到 for “arrive at”
  
  • Often emphasizes arrival or completion.

Examples:

• 我想回家休息。= I want to go home and rest. (normal)
• 回到家以后，我就睡觉了。= After I got back home, I went to sleep.

In your sentence, 回家 is the natural, everyday choice.

In 回家休息, 休息 is a verb, meaning “to rest.”

Chinese often uses two verbs in a row to show a purpose or sequence:

• 回家休息 = go home (and) rest
• 去公园散步 = go to the park (and) take a walk

You can add a little word to make it sound lighter or shorter:

• 回家休息一下。= go home and rest a bit / have a little rest.

休息 can also be a noun in other contexts:

• 我需要一个休息。= I need a rest.

But in your sentence it’s clearly functioning as a verb.

Without 了, the sentence can naturally be understood as describing a general or typical situation (habit / tendency):

很多同学下课以后去聚会，可是我想回家休息。
Many classmates (usually / often) go to parties after class, but I (usually) want to go home and rest.

If you wanted to make it clearly about a specific future occasion, you might add other markers (like 会, “will”) or time words:

• 明天很多同学下课以后会去聚会，可是我想回家休息。
  = Tomorrow many classmates will go to a party after class, but I want to go home and rest.

You don’t need 了 here unless you’re emphasizing completion or a change of state, which isn’t the focus.

Normally, no. In this sentence, the second clause introduces a different subject (“I”) from the first clause (“many classmates”), so the subject must be stated:

• 很多同学下课以后去聚会，可是我想回家休息。

If the subject of the second clause were obviously the same as the first, you could often omit it, but here the contrast depends on keeping 我 (“but I…”).

Dropping 我 would sound incomplete and unclear.

Yes. In Chinese writing, it’s common to use a comma (，) to connect closely related clauses, including ones linked by words like 可是 / 但是 / 不过:

• 他想去，可是没有时间。
• 很多同学下课以后去聚会，可是我想回家休息。

You generally don’t put a period before 可是; you treat it more like “but” in English in the middle of a sentence, not like starting a brand-new sentence with “But.”