Learn Hardcore Swedish: Jag tror att hans chef har ett möte. - I believe that his boss has a meeting.

Both are fine. Jag tror att hans chef har ett möte is slightly more formal/neutral. In everyday speech, many people drop att: Jag tror hans chef har ett möte. The word order in the clause stays the same either way (subject before the verb: hans chef har).

Why is it att hans chef har and not att har hans chef?

After att (a subordinate clause), Swedish does not use verb-second. The finite verb comes after the subject: att [subject] [verb] → att hans chef har.... Putting the verb before the subject here (att har hans chef...) is ungrammatical in standard Swedish.

Why is there no article before chef? Why not hans en chef or hans chefen?

In Swedish, possessives (like hans, hennes, min, vår) replace the article. So you say hans chef, not hans en chef or hans chefen. Compare:

en chef = a boss
chefen = the boss
hans chef = his boss (no article, no definite ending)

Why is it ett möte and not en möte?

Because möte is a neuter noun. Its forms are:

singular: ett möte
definite singular: mötet
plural: möten
definite plural: mötena

Can I say har möte without ett?

Yes. Ha möte is common and idiomatic, often meaning “be in a meeting” or “have a meeting (scheduled).” Nuances:

har ett möte = has one specific meeting (counting it)
har möte / sitter i möte = is in a meeting (right now) or generally has a meeting

Should I use tror, tycker, or tänker?

tror = think/believe about facts you’re unsure about (best here)
tycker = think/hold an opinion (subjective judgment)
tänker = think in the sense of “intend/plan” or “be thinking” Examples:
Jag tror att hans chef har ett möte. (belief about a fact)
Jag tycker att mötena är onödiga. (opinion)
Jag tänker ha ett möte imorgon. (plan)

How do I negate this? Where does inte go?

Main clause: Jag tror inte att ...
In the subordinate clause: att hans chef inte har ... Examples:
Jag tror inte att hans chef har ett möte.
Jag tror att hans chef inte har (något) möte.

What if I mean “if/whether,” not “that”?

Use om, not att:

Jag undrar om hans chef har ett möte. = I wonder if his boss has a meeting.

How is att pronounced? It sometimes sounds like “å.”

In casual speech, att (both the “that” conjunction and the “to” infinitive marker) is often reduced, commonly sounding like å or just a. In careful speech, you’ll hear a clearer att.

Pronunciation tips for tricky words here?

Jag ≈ “yah” (the final g is often very soft or silent)
chef: the ch is the Swedish “sj”-sound (a husky “sh” from the back of the mouth), then long e: roughly “shehf”
möte: ö like French “peu”; roughly “MEU-teh” (with long vowel in the first syllable)
att often reduced as above
har as written, with a clear r

Why hans and not sin/sitt/sina?

Use sin/sitt/sina only when the possessor is the subject of the same clause. Here, inside the att-clause, the subject is hans chef, so sin can’t refer back to someone in the main clause. Therefore hans is correct. For comparison:

Same clause: Han gillar sin chef. (his own boss)
Across att: Han tror att hans chef har ett möte. (“his” = some male person, often him, but context decides; you cannot use sin here)

What if the person isn’t male, or I want a gender-neutral form?

Female: hennes (her)
Plural: deras (their)
Gender-neutral singular (informal but increasingly common): hen (subject), hens (possessive)
Formal/thing-like “its”: dess Example: Jag tror att hens chef har ett möte.

Does the present tense har mean “has now” or can it be future too?

Both are possible. Present can express current action or a scheduled/arranged near-future:

Now: Jag tror att hans chef har möte (just nu).
Scheduled: Jag tror att hans chef har ett möte klockan tre. To be explicit about future, use ska: ... ska ha ett möte.

How do I say it in the past: “I thought his boss had a meeting”?

Jag trodde att hans chef hade ett möte.

tro → tror, trodde, trott
ha → har, hade, haft

How do I turn this into a question like “Do you think his boss has a meeting?”

Yes/no question: Tror du att hans chef har ett möte?
Or ask directly about the subordinate clause: Har hans chef ett möte?

Why isn’t it att hans chef ha ett möte?

Because Swedish subordinate clauses need a finite verb. Here you need the present har, not the infinitive ha. Use ha only after auxiliaries/modals like ska, vill, kan: att hans chef ska ha ett möte.

Do I put a comma before att?

No comma in modern standard Swedish: Jag tror att ... (no comma). Commas before att are generally avoided unless you’re marking a clear parenthetical or special rhythm in stylistic writing.