Jag hittar inte mina hörlurar, så jag kan inte lyssna på musik på bussen.

In Swedish, each finite verb normally needs an explicit subject. After the comma, så starts a new clause (så jag kan inte …), and that clause still needs its own subject, so you repeat jag.
You generally can’t omit it the way you sometimes can in English (e.g., “...so can’t listen...” is informal). Swedish would sound incomplete without jag.

Inte is the standard negation word (not). Its position depends on clause type:

• In a main clause (like Jag hittar inte mina hörlurar), inte typically comes after the finite verb (hittar).
• In subordinate clauses, it usually comes before the finite verb.
  Here both clauses are main clauses, so hittar inte and kan inte are the expected word orders.

Hittar is the present tense form of att hitta (to find). Swedish present tense is used for:

• what’s happening now (“I can’t find…”),
• general statements (“I don’t find…” as a habit, depending on context).
  In this sentence it’s clearly “right now”: Jag hittar inte …

Both are common, with a slight nuance:

• Jag hittar inte mina hörlurar = “I can’t find my headphones” (I’m not managing to locate them / they aren’t turning up).
• Jag kan inte hitta mina hörlurar = also “I can’t find…”, slightly more explicitly “I’m unable to find…”.
  In everyday speech, Jag hittar inte… is very natural.

Yes: så often means so/therefore, linking cause → result:

• “I can’t find my headphones, so I can’t listen to music…”
  It introduces a new main clause after a comma, which is why you get normal main-clause word order after it (så jag kan inte…).

Often, yes:

• Jag hittar inte mina hörlurar, därför kan jag inte lyssna på musik på bussen.
  But note the word order: after därför in a main clause, Swedish typically has inversion (the verb comes before the subject): därför kan jag inte… (not därför jag kan…).
  With så, you usually keep så jag kan….

Because hörlurar is plural. Swedish possessives agree with number:

• min = my (common gender singular)
• mitt = my (neuter singular)
• mina = my (plural)
  So: mina hörlurar = “my headphones.”

The base singular is en hörlur (common gender). The plural is hörlurar.
In practice, people often talk about headphones in the plural (hörlurar) because it’s a pair, but you can use singular if you mean one earpiece: en hörlur.

In Swedish, lyssna usually takes the preposition på for what you’re listening to:

• lyssna på musik = listen to music
• lyssna på radio/podcasten = listen to the radio/podcast
  So på is required by the verb pattern lyssna på + noun.

After modal verbs like kan (can), Swedish uses the infinitive form of the next verb (without att in most cases):

• kan lyssna (can listen)
  Not kan lyssnar. Lyssnar would be present tense, but modals require the infinitive.

Swedish commonly uses på with public transport:

• på bussen, på tåget, på flyget = on the bus/train/plane
  English often says “on the bus” too, but even where English might say “in,” Swedish still prefers på for being a passenger using that means of transport.

Swedish often uses the definite form for something specific in the situation (“the bus I’m taking / the bus in question”):

• på bussen feels like “on the bus (I’m on / the bus ride).”
  You can say på en buss, but it’s more like “on a (random) bus” or “on a bus (somewhere),” less specific.

Yes, Swedish allows flexibility with adverbials:

• … så jag kan inte lyssna på musik på bussen. (neutral)
• … så jag kan inte på bussen lyssna på musik. (possible but sounds a bit marked/awkward)
• … så jag kan inte lyssna på musik när jag är på bussen. (more explicit: “when I’m on the bus”)
  The given order is the most natural.

It’s standard to separate two main clauses with a comma when the second clause is introduced by a connector like så:

• Jag hittar inte mina hörlurar, så jag kan inte…
  In informal writing, people sometimes omit commas, but the comma here is normal and helpful.

In most contexts it means “I can’t find my headphones / I’m not finding them.”
If you meant “I don’t find my headphones (to be…)” as an opinion, Swedish would use different structures, e.g.:

• Jag tycker inte att mina hörlurar är bra. (I don’t think my headphones are good.)
  So the “searching but failing” reading is the default.

Hittade is past tense:

• Jag hittade inte mina hörlurar, så jag kunde inte lyssna… = “I didn’t find my headphones, so I couldn’t listen…”
  Note you’d normally match the tense in the second clause too: kunde inte instead of kan inte.

Yes, depending on what you mean:

• hörlurar = headphones (general)
• in-ear-hörlurar = in-ear headphones
• öronsnäckor = earbuds/earphones (common everyday term)
  You could say: Jag hittar inte mina öronsnäckor… if that fits better.