Die Ananas auf dem Tisch riecht süß und frisch.

Ananas is a feminine noun in German, so its nominative singular article is die.

• die Ananas = the pineapple

This is something you usually just have to learn with the noun. German noun gender often does not match what an English speaker expects.

Because the subject is die Ananas, which is third person singular.

The verb riechen is conjugated like this in the present tense:

• ich rieche
• du riechst
• er/sie/es riecht
• wir riechen
• ihr riecht
• sie/Sie riechen

So die Ananas takes riecht.

Dem Tisch is dative.

That is because auf is a two-way preposition. It can take:

• accusative when there is movement toward a destination
• dative when there is location and no movement

Here, the pineapple is already on the table, so this is a location, not movement:

• auf dem Tisch = on the table

Compare:

• Die Ananas liegt auf dem Tisch. = location → dative
• Ich lege die Ananas auf den Tisch. = movement onto the table → accusative

Because this sentence describes where the pineapple is, not where it is being moved.

• auf dem Tisch = on the table, already there
• auf den Tisch = onto the table, moving there

So in your sentence, auf dem Tisch is correct because it answers Where is the pineapple?

Because they are not directly in front of a noun here. They are being used as predicate adjectives after the verb riechen.

In German, predicate adjectives do not take endings:

• Die Ananas ist süß.
• Die Ananas riecht süß und frisch.

But when an adjective comes before a noun, it does take an ending:

• die süße Ananas
• eine frische Ananas

So:

• süß und frisch = no endings, because they come after the verb

Grammatically, they describe how it smells.

So Die Ananas riecht süß und frisch means that the pineapple gives off a smell that is sweet and fresh.

In practice, this also suggests something about the pineapple itself, but the sentence is specifically about its smell, not directly saying The pineapple is sweet and fresh.

German main clauses usually put the conjugated verb in second position.

Here the structure is:

• Die Ananas auf dem Tisch = the subject phrase
• riecht = the finite verb
• süß und frisch = the rest of the sentence

So the verb riecht is in the normal second position.

Also, auf dem Tisch is part of the subject phrase description here, telling you which pineapple we are talking about: the one on the table.

Yes, that is possible.

German lets you move elements to the front for emphasis, as long as the finite verb stays in second position:

• Die Ananas auf dem Tisch riecht süß und frisch.
• Auf dem Tisch riecht die Ananas süß und frisch.

The second version puts more emphasis on the location on the table.

However, the original version may sound a bit more natural if you want auf dem Tisch to identify the pineapple.

Because und is simply joining two equal adjectives:

• süß
• frisch

In German, you normally do not use a comma before und when it connects words or phrases in a simple list.

So:

• süß und frisch = correct

It is singular here.

You can tell because:

• the article is die for feminine singular
• the verb is riecht, which is singular

If it were plural, the verb would be riechen:

• Die Ananas riechen süß und frisch.

In real usage, Ananas can also be a plural form, so the verb often helps you see whether it is singular or plural.

Usually, yes, but English uses smell in two ways, and German does something similar.

Riechen can mean:

1. to have a smell / to smell like something

   • Die Ananas riecht süß.

2. to smell something with your nose

   • Ich rieche die Ananas.

So the verb can be either:

• intransitive: something smells a certain way
• transitive: someone smells something

The meaning depends on the sentence structure.

Yes, but that changes the structure slightly.

German often uses riechen nach + dative to say something smells like something:

• Die Ananas riecht nach Sommer.
• Die Ananas riecht nach Zucker.

Your sentence uses adjectives instead:

• Die Ananas riecht süß und frisch.

So both are possible, but they express the smell in different ways:

• riecht süß und frisch = smells sweet and fresh
• riecht nach X = smells like X

A useful breakdown is:

• Die Ananas = subject
• auf dem Tisch = prepositional phrase describing location / helping identify the noun
• riecht = finite verb
• süß und frisch = predicate adjectives

So you can think of the whole sentence as:

• [The pineapple on the table] [smells] [sweet and fresh].

This is a very common German pattern: subject + verb + predicate adjective(s).