Jag lånar hörluren i tio minuter, och sedan ger jag den tillbaka.

Swedish låna can mean both borrow and lend depending on perspective. In Jag lånar hörluren, the subject (jag) is the one who will use the item temporarily, so in natural English it’s I’m borrowing the headphone/earpiece.
If you want to be unambiguous, Swedish often uses:

• låna (av) = borrow (from someone): Jag lånar hörluren av dig.
• låna ut = lend: Jag lånar ut hörluren till dig.

Hörlur is a common-gender noun (en hörlur). Swedish often attaches the definite article to the end of the noun:

• en hörlur = a headphone/earpiece
• hörluren = the headphone/earpiece

Here it implies a specific one that both speakers know about (e.g., your headphone or the one on the table).

Yes, hörluren is singular: the headphone/earpiece. Swedish can talk about one earbud/headphone as a single unit.
Common alternatives:

• hörlur (singular) / hörlurar (plural) = headphone(s)/earbuds
• Jag lånar hörlurarna… = I’ll borrow the headphones… (both)

So the sentence suggests you’re borrowing one earpiece/earbud (or treating the set as one item in context).

Swedish commonly uses i to express duration with time spans:

• i tio minuter = for ten minutes
• i två timmar = for two hours

It’s a fixed, very common way to say “for (a period of time).”

No. They refer to different time meanings:

• i tio minuter = for ten minutes (duration)
• om tio minuter = in ten minutes (from now; time until something happens)

So Jag lånar hörluren i tio minuter = I’ll have it for ten minutes.
Jag ger den tillbaka om tio minuter = I’ll give it back in ten minutes.

You don’t strictly need both, but och sedan is very natural in speech: and then.
Alternatives:

• Jag lånar … i tio minuter och ger den sedan tillbaka. (more compact)
• Jag lånar … i tio minuter. Sedan ger jag den tillbaka. (two sentences; slightly more emphatic)

In Swedish, object pronouns like den typically come before particles like tillbaka:

• ge den tillbaka = give it back (standard)
• ge tillbaka den sounds unnatural with a pronoun (though with a full noun it can work in some styles: ge tillbaka hörluren)

So pronoun order is a key rule of thumb: verb + pronoun object + particle.

Tillbaka means back (returning something to the previous owner/place).
In ge … tillbaka, it forms the common verb phrase give back/return. You can also say:

• lämna tillbaka = give back/return (often more common for returning items)
• ge tillbaka = give back (can feel a bit more direct)

Swedish pronouns agree with the noun’s grammatical gender:

• en-words → den
• ett-words → det

Since hörlur is en hörlur, the pronoun is den: Jag ger den tillbaka.

Yes. sen is a very common spoken/less formal form of sedan. Both mean then.

• sedan = more neutral/formal in writing
• sen = informal/colloquial, common in conversation and informal text

Both are fine. With a comma, it reads as one flowing statement:

• Jag lånar …, och sedan … = one combined thought

As two sentences, it can sound slightly clearer or more deliberate:

• Jag lånar hörluren i tio minuter. Sedan ger jag den tillbaka.

Swedish punctuation is fairly flexible here; choice often depends on style.

Your sentence is already natural. Two very common variations are:

• Jag lånar hörluren i tio minuter, och sedan lämnar jag tillbaka den.
• Jag lånar hörluren i tio minuter och lämnar den tillbaka sen.

Lämna tillbaka is extremely common for returning borrowed items, but ge … tillbaka is also correct.