Learn Hardcore Chinese: tā qíshí yǐwéi wǒ bú huì lái, kěshì wǒ yǐjīng dào le. - He actually thought I wouldn’t come, but I’ve already arrived.

以为 (yǐwéi) usually suggests a belief that turns out to be incorrect or is contradicted by new information. In the sentence, it’s shown wrong by “but I’ve already arrived.”
认为 (rènwéi) is a neutral “to believe/hold the opinion,” often more formal.
觉得 (juéde) is “to feel/think” (subjective impression), no right/wrong nuance.
想 (xiǎng) is “to think/wonder/consider” or “to want to,” focusing on mental activity or intention. Examples:
我以为你不来，结果你到了。
我认为这个办法可行。
我觉得这个菜很好吃。
我想明天去。

Why use 不会来 here? Could it be 不来, 不能来, or 来不了?

不会来 (bú huì lái) = “won’t/wouldn’t come,” a prediction/assumption about the future or likelihood.
不来 (bù lái) = “won’t come” (decision/refusal) or “doesn’t come” (habit); also works here, a bit more direct about intention.
不能来 (bù néng lái) = “cannot come” (not allowed/able due to rules or conditions).
来不了 (lái bu liǎo) = “can’t make it” (practically impossible due to obstacles). He “thought I wouldn’t come” is most naturally 不会来 or 不来. If you mean “he thought I couldn’t come,” use 不能来/来不了.

In 不会, why is 不 pronounced bú instead of bù?

Tone sandhi: 不 (bù) changes to rising tone bú before a fourth-tone syllable. 会 (huì) is fourth tone, so you get bú huì. More examples: bú yào, bú shì, bú duì. Otherwise, 不 stays bù (e.g., bù lái, bù néng).

What does 其实 (qíshí) add, and where can it go in the sentence?

其实 means “actually/in fact,” often used to correct or contrast expectations.
Placement:
- 他其实以为… emphasizes “he actually (surprisingly) thought…”
- 其实，他以为… frames the whole statement as a correction or new angle.
- Avoid 他以为我其实不会来 here, because that would mean “he thought that actually I wouldn’t come,” which conflicts with the second clause where you did arrive.

How is 可是 (kěshì) different from 但是 (dànshì) and 不过 (búguò)?

All mean “but/however,” and all work here.
可是 is very common in speech and can feel a bit more emotive.
但是 is slightly more neutral/formal.
不过 is lighter (“however/only that”), often softening the contrast. Examples:
他以为我不会来，可是我已经到了。
他以为我不会来，但是我已经到了。
他以为我不会来，不过我已经到了。

Why is 已经 (yǐjīng) paired with 了 (le)? Is 了 required?

已经 highlights completion (“already”). With dynamic events like arriving, native speech almost always uses perfective 了: 我已经到了.
With stative verbs, 已经 may or may not take 了, depending on whether you’re emphasizing a new state:
- 我已经知道。= I already know (state).
- 我已经知道了。= I’ve now come to know (newly changed state).
For arrival, 我已经到 is unnatural; use 我已经到了 (or specify a place: 我已经到学校了).

What exactly does 了 do in 我已经到了? Is it the same as sentence-final 了?

Here 了 is the perfective particle marking completion of the verb 到 (“arrive”): “I have arrived.”
It happens to be at the end of the sentence, but functionally it’s the verb-completion 了, not the sentence-final “new situation” 了.
Test: add an object or place and it stays the same role: 我已经到这儿了 / 我已经到公司了.

Should I say 我已经到了 or 我已经来了 when telling someone I’ve arrived?

For arrival updates (texts/calls), the default is 我已经到了 (“I’ve arrived [at the agreed place]”).
我来了 is used when you show up and announce yourself (“Here I am!/I’m coming!”). 我已经来了 is possible but often means “I came earlier (than you think),” less idiomatic for a check-in message.

Why use 到 as the verb instead of 来到 or 到达? Do I need to name the place?

到 (dào) as a verb = “arrive,” neutral and common: 我到了 / 我到学校了.
来到 (lái dào) tends to be used with an explicit place and feels a bit more narrative: 我来到学校了 (OK), but bare 我已经来到 sounds incomplete.
到达 (dàodá) is formal/literary: 航班到达北京.
You can omit the place if it’s contextually clear: 我已经到了 = “I’ve arrived (here/there).”

If I want to say “He thought I didn’t come” (past), how would I say it? What about “but I had already arrived (by then)”?

“He thought I didn’t come”: 他以为我没来。
“But I had already arrived (by then)”: add a time anchor:
- 可是我那时已经到了。
- 可我早就到了。 (emphasizes “long before”)

Can I drop the second 我 and just say “…可是已经到了”?

Usually no. The subject switches from 他 to 我 across the comma. Dropping 我 makes it unclear who arrived. Keep 可是我已经到了. Subject drop is fine only when the subject remains the same or is unmistakable from context.

Can I move 其实 to the very beginning: 其实，他以为…? Any nuance?

Yes. 其实，他以为我不会来 is natural and frames the whole statement as a corrective aside. 他其实以为… slightly highlights the unexpectedness of his belief. Both are common; the difference is subtle emphasis.

Can I add 的 after the clause with 以为, like 他以为我不会来的?

Yes. Ending the belief-clause with 的 can soften or package it as a definite assumption: 他以为我不会来的. Both versions are fine; with 的 often sounds a bit more colloquial/emphatic about the assumed content.

Can 以为 take 了 or 过 (e.g., 他以为了…)? How do I mark the time of the thinking?

Don’t attach 了/过 directly to 以为 in this use. Instead, use time expressions:
- 他当时以为… (at that time)
- 他原来/本来以为… (originally)
- 他一直以为… (had always thought) These adverbs handle pastness, change, or duration of the belief.

What meaning does 会 (huì) have here—“will,” “can,” or “be likely to”? How is it different from 要?

Here 会 = “will/would” or “be likely to”: 不会来 = “won’t/wouldn’t come.”
会 can also mean “know how to” (skill), but with 来 it’s not the skill reading.
要 (yào)
- verb often signals plan/arrangement/near future or strong inevitability: 他以为我要来 = “He thought I was going to come (planned).” 不会来 is about likelihood; 不想来/不来 is about intention.

Is 已经 redundant here? What changes if I remove it?

我到了 = “I arrived/I’ve arrived.” Clear and correct.
我已经到了 adds emphasis to the timing (“I’ve already arrived,” often earlier than someone thought). In this contrastive sentence, 已经 strengthens the rebuttal to his assumption.

Could I say 到过 here?

No. 到过 is the experiential “have been to (at some point before),” not a fresh arrival. 我到过北京 = “I have been to Beijing (before).” For “I’ve arrived (now),” use 到了.