Jeg lægger sokkerne i vaskekurven og folder håndklæderne, før jeg går i seng.

Because at lægge and at ligge are different verbs.

• at lægge = to lay / put something somewhere
• at ligge = to lie / be lying

Here the speaker is actively putting the socks into the laundry basket, so Danish uses lægger.

Compare:

• Jeg lægger sokkerne i vaskekurven. = I put the socks in the laundry basket.
• Sokkerne ligger i vaskekurven. = The socks are lying in the laundry basket.

They are definite nouns.

In Danish, the is usually added to the end of the noun instead of being a separate word.

• sokker = socks → sokkerne = the socks
• håndklæder = towels → håndklæderne = the towels
• vaskekurv = laundry basket → vaskekurven = the laundry basket

So English uses a separate word, the, but Danish often uses endings like:

• -en
• -et
• -ne

Because Danish forms many compound nouns.

Vaskekurv is made from:

• vask(e) = wash / washing
• kurv = basket

So vaskekurv literally means something like washing basket, i.e. laundry basket.

Then the definite ending is added to the whole word:

• vaskekurv = a laundry basket
• vaskekurven = the laundry basket

This is very normal in Danish.

Because the same subject, jeg, applies to both verbs.

So:

• Jeg lægger sokkerne i vaskekurven og folder håndklæderne

means:

• I put the socks in the laundry basket and fold the towels

Danish does not need to repeat jeg here, just like English usually does not repeat I in the same structure.

They are all present tense forms.

• at lægge → lægger
• at folde → folder
• at gå → går

For many Danish verbs, the present tense ends in -r.

So this sentence is talking about what the speaker does, either as a present action or as a routine/habit.

In Danish, i can cover both ideas, depending on context.

Here, with lægger, it means placement, so i vaskekurven is understood as into / in the laundry basket.

Danish does not always make the same clear distinction that English makes between in and into. The verb often tells you whether the meaning is movement or location.

So:

• lægger ... i vaskekurven = puts ... into the laundry basket
• ligger i vaskekurven = is in the laundry basket

Because før here introduces a full clause, not an infinitive.

A full clause needs:

• a subject: jeg
• a finite verb: går

So:

• før jeg går i seng = before I go to bed

You use at with an infinitive, but that is a different structure.

Compare:

• Jeg prøver at gå i seng tidligt. = I try to go to bed early.
• Jeg folder håndklæderne, før jeg går i seng. = I fold the towels before I go to bed.

Because før introduces a subordinate clause.

In Danish subordinate clauses, the normal order is:

• subject + verb

So:

• før jeg går i seng

is correct.

If you put that whole før-clause at the beginning of the sentence, then the main clause changes word order because Danish main clauses follow the verb-second rule:

• Før jeg går i seng, lægger jeg sokkerne i vaskekurven og folder håndklæderne.

Notice the inversion in the main clause:

• lægger jeg, not jeg lægger

Because gå i seng is an idiomatic expression, like English go to bed.

It refers to the general act of going to bed, not to a specific bed as a physical object. That is why Danish uses seng, not sengen.

So:

• gå i seng = go to bed

But if you were talking about a specific bed, you could use the definite form in another kind of sentence, for example:

• Sengen står ved vinduet. = The bed is by the window.

You can break it down into parts:

• hånd = hand
• klæde = cloth

Together:

• håndklæde = towel

Then Danish adds the plural and definite endings:

• håndklæde = a towel
• håndklæder = towels
• håndklæderne = the towels

So even though the word looks long, it is built in a very regular Danish way.

Yes, especially these:

• æ in lægger and håndklæderne
• å in går and hånd
• unstressed endings like -er and -erne

Very roughly:

• æ is somewhat like the vowel in English cat, but not exactly
• å is somewhat like the vowel in law or more, depending on accent
• unstressed -er often sounds weak, almost like uh

Also, Danish pronunciation is often much softer than the spelling suggests, so it is best to learn these words by listening as well as reading them.