A estufa fica ao lado da horta.

Here, estufa means greenhouse.

In other contexts, estufa can also refer to a heated enclosure, a kiln, or even a kind of stove/heater, depending on the situation. But with horta in the same sentence, greenhouse is clearly the intended meaning.

A is the feminine singular definite article, meaning the.

So:

• a estufa = the greenhouse

Portuguese uses definite articles much more often than English does, so seeing a or o before nouns is very normal.

Not exactly. Ficar has several meanings in Portuguese, and one very common one is to be located.

So in this sentence, fica means something like:

• is
• is located
• stands

This is very common in Portuguese when talking about where something is situated:

• Lisboa fica em Portugal.
• A escola fica perto da estação.

So although ficar can sometimes mean to stay, that is not the best interpretation here.

In European Portuguese, ficar is very natural for giving the location of something as a general fact.

• A estufa fica ao lado da horta. = the greenhouse is located next to the vegetable garden.

If you say está, the sentence is still possible and understandable:

• A estufa está ao lado da horta.

But fica often sounds better when you mean a more stable or usual location, while está can sound a bit more like describing where something is at the moment.

Ao lado de is a fixed expression meaning:

• next to
• beside
• by the side of

In the sentence, it appears as ao lado da horta because of contractions:

• ao = a + o
• da = de + a

So:

• ao lado da horta = next to the vegetable garden

You should learn ao lado de as one whole expression.

Because horta is a feminine noun, and Portuguese normally uses the definite article here:

• a horta = the vegetable garden

When de comes before a, they contract:

• de + a = da

So:

• ao lado da horta = next to the vegetable garden

Not quite.

• horta = a vegetable garden, kitchen garden, or allotment-like growing area
• jardim = a garden in the more general or ornamental sense

So horta suggests a place where vegetables, herbs, and other edible plants are grown, not just flowers or decorative plants.

The word order is quite close to English:

• A estufa = the greenhouse
• fica = is located / is
• ao lado da horta = next to the vegetable garden

So the structure is:

• subject + verb + location phrase

This is a very normal and basic Portuguese sentence pattern.

A rough European Portuguese pronunciation is:

• A estufa fica ao lado da horta
• approximately: uh esh-TOO-fuh FEE-kuh ow LAH-doo duh OR-tuh

A few useful notes:

• estufa has the stress on tu
• the h in horta is silent
• in European Portuguese, unstressed vowels are often reduced, so some final a sounds are weaker than in Brazilian Portuguese

A more IPA-like version would be close to:

• [ɐ ʃˈtufɐ ˈfikɐ aw ˈladu dɐ ˈɔɾtɐ]

Yes, you can, and it will be understood perfectly.

But the nuance is slightly different:

• fica = is located, is situated
• está = is, is positioned

For a general description of where something is, fica is often the more natural choice. So the original sentence is a very good model to learn.