De zwelling bleef rood en pijnlijk.

Zwelling is a de-word. In Dutch, every noun takes either de or het, and this has to be learned with the noun.

A useful pattern: many nouns ending in -ing are de-words, so de zwelling fits that pattern.

Examples:

• de wandeling
• de vergadering
• de oplossing
• de zwelling

Zwelling is a noun meaning swelling.

It comes from the verb zwellen, which means to swell.

So the relationship is:

• zwellen = to swell
• de zwelling = the swelling

This is similar to English pairs like:

• to improve → improvement
• to swell → swelling

Bleef is the simple past singular of blijven.

Forms of blijven:

• infinitive: blijven
• present: ik blijf, jij blijft, hij/zij blijft
• past singular: bleef
• past plural: bleven
• past participle: gebleven

In this sentence, bleef means remained or stayed:

• De zwelling bleef rood en pijnlijk.
• The swelling remained red and painful.

Dutch blijven often works like English remain when it is followed by an adjective.

Pattern:

• blijven + adjective

Examples:

• Hij bleef rustig. = He remained calm.
• De deur bleef open. = The door remained open.
• De zwelling bleef rood. = The swelling remained red.

So in this sentence, bleef describes a continuing state, not physical staying in a place.

Because they come after the verb and describe the subject, not directly the noun.

This is called a predicative adjective. In Dutch, predicative adjectives usually do not take the -e ending.

Compare:

Attributive adjective: directly before the noun

• de rode plek = the red spot
• de pijnlijke zwelling = the painful swelling

Predicative adjective: after a verb like zijn, worden, blijven

• De plek is rood.
• De zwelling bleef pijnlijk.

So:

• de rode zwelling = the red swelling
• de zwelling bleef rood = the swelling remained red

This is normal Dutch main-clause word order:

subject + finite verb + rest

So:

• De zwelling = subject
• bleef = finite verb
• rood en pijnlijk = complement

This is very common in Dutch:

• Hij is moe.
• Het water werd koud.
• De zwelling bleef rood en pijnlijk.

If you changed the order for emphasis, the verb would still stay in second position in a main clause:

• Rood en pijnlijk bleef de zwelling.
  This is possible, but much less neutral.

Yes, you can say that, but the meaning is slightly different.

• De zwelling was rood en pijnlijk.
  This simply states that the swelling was red and painful.

• De zwelling bleef rood en pijnlijk.
  This suggests that the swelling continued to be red and painful, often despite time passing or despite expectation that it might improve.

So bleef adds the idea of persistence or lack of change.

Yes. Rood and pijnlijk are two coordinated adjectives joined by en.

Both describe de zwelling:

• it was red
• it was painful

Dutch often does this exactly like English:

• lang en dun = long and thin
• warm en droog = warm and dry
• rood en pijnlijk = red and painful

Approximate pronunciation:

• zwelling: roughly ZVEL-ling
  The zw at the start can be tricky for English speakers. The w is Dutch, not quite like English w.

• bleef: roughly blayf
  The ee sounds like the vowel in English day, but without the English glide being too strong.

• pijnlijk: roughly PIHN-lək
  The first part pijn sounds somewhat like pine. The final -lijk is often reduced in everyday speech.

A careful learner tip:

• ij in pijnlijk is an important Dutch vowel spelling and often sounds somewhat like English eye.

Usually yes, but the exact English translation depends on context.

Pijnlijk can mean:

• painful in a physical sense
• sometimes painful or awkward/embarrassing in a figurative sense

Examples:

• een pijnlijke wond = a painful wound
• een pijnlijk gesprek = a painful conversation

In your sentence, because it is about de zwelling, the physical meaning is clearly intended.

Yes:

• De zwelling blijft rood en pijnlijk.

That means:

• The swelling remains red and painful or
• The swelling is staying red and painful

Compare:

• bleef = remained / stayed, past
• blijft = remains / stays, present

So the tense changes, but the structure stays the same.