Jag lade två skivor bröd i brödrosten medan hon hällde upp te.

Because the verb lägga (to lay / put) is irregular in the past tense.

Its main forms are:

• infinitive: lägga
• present: lägger
• past: lade
• supine: lagt

So:

• Jag lägger brödet i brödrosten = I put the bread in the toaster
• Jag lade brödet i brödrosten = I put the bread in the toaster

A common learner mistake is to build the past tense from the present stem and guess läggde, but Swedish does not do that here.

Yes. La is a very common alternative to lade in everyday Swedish.

So both of these are possible:

• Jag lade två skivor bröd i brödrosten
• Jag la två skivor bröd i brödrosten

In general:

• lade can sound a bit more formal or careful
• la is very common in speech and informal writing

Both are correct and useful to recognize.

Both are possible, but they are structured differently.

• två skivor bröd = two slices of bread
• två brödskivor = two bread slices

The first one is often the most natural when you are talking about quantity in a straightforward way. It works like a measure expression:

• ett glas vatten = a glass of water
• en kopp kaffe = a cup of coffee
• två skivor bröd = two slices of bread

The compound noun brödskivor also exists, but in this sentence skivor bröd sounds very natural.

Swedish often leaves out of in this kind of expression.

Compare:

• English: two slices of bread
• Swedish: två skivor bröd

This is very common with quantities and containers:

• ett glas mjölk = a glass of milk
• en kopp te = a cup of tea
• en bit ost = a piece of cheese

So skivor bröd is completely normal Swedish grammar.

Swedish loves compound nouns, so words that are separate in English are often written as one word in Swedish.

• bröd = bread
• rost = roast / toast-related element
• brödrost = toaster
• brödrosten = the toaster

The ending -en is the definite article attached to the noun:

• en brödrost = a toaster
• brödrosten = the toaster

So i brödrosten means in the toaster.

Because the bread goes into the toaster, not on it.

• i = in / into
• på = on / onto

With a typical pop-up toaster, Swedish uses i brödrosten because the slices are inserted inside it.

Examples:

• Jag lade brödet i ugnen = I put the bread in the oven
• Jag lade boken på bordet = I put the book on the table

So i is the natural choice here.

Medan means while.

It introduces a subordinate clause and shows that two actions were happening at the same time:

• Jag lade två skivor bröd i brödrosten
• medan hon hällde upp te

So the idea is:

• I put two slices of bread in the toaster
• while she was pouring tea

It is used much like English while.

Other examples:

• Jag lagade mat medan hon dukade bordet.
• Han läste medan jag skrev.

Because hälla upp is a very common verb phrase meaning to pour (out/up), especially into cups or glasses for serving.

• hälla = to pour
• hälla upp = to pour out / pour into cups or glasses / serve by pouring

So:

• hon hällde upp te suggests she was pouring tea, probably into cups
• plain hon hällde te is possible in some contexts, but it does not sound as complete or as natural here

The particle upp often changes or sharpens the meaning of the verb, and Swedish uses these particle verbs a lot.

It usually suggests pouring tea for serving, not just making tea in a general sense.

So it often implies something like:

• pouring tea from a teapot into cups
• serving the tea

That is why hälla upp fits very well in an everyday scene like this one.

If the sentence had gjorde te, that would mean made tea.
If it had serverade te, that would mean served tea more generally.
But hällde upp te gives the more specific image of the pouring action.

Because te is being used as an uncountable substance noun, like tea in English.

Compare:

• hon hällde upp te = she poured tea
• hon drack kaffe = she drank coffee
• vi köpte mjölk = we bought milk

You do not need an article when you mean the substance in a general amount.

If you wanted to be more specific, you could add other words:

• hon hällde upp ett te would usually not sound right in this context
• hon hällde upp en kopp te = she poured a cup of tea
• hon hällde upp teet = she poured the tea

So zero article is normal here.

Because medan introduces a subordinate clause, and in Swedish subordinate clauses the subject usually comes before the finite verb:

• medan hon hällde upp te

That is the normal order:

• medan
  • subject
    • verb

This is different from main clauses, where Swedish often has verb-second word order.

For example:

• main clause: Hon hällde upp te.
• subordinate clause: ... medan hon hällde upp te.

So the word order here is exactly what you should expect after medan.

Yes. If the subordinate clause comes first, the main clause has inversion, because Swedish main clauses keep the finite verb in second position.

So you could say:

• Medan hon hällde upp te lade jag två skivor bröd i brödrosten.

Notice the order in the main clause:

• lade jag not
• jag lade

That happens because the sentence begins with the medan clause, which takes the first position, so the finite verb in the main clause comes next.

It is the right word here.

• en skiva = a slice
• två skivor = two slices

It is commonly used for things like:

• bröd = bread
• ost = cheese
• skinka = ham
• citron = lemon

So två skivor bröd is exactly the kind of phrase where skiva is used naturally.