Det finns ett lågt staket runt gården, och grinden är nästan alltid öppen på eftermiddagen.

Det finns is the normal Swedish way to say there is or there are when you introduce something that exists or is present somewhere.

• det here is a dummy subject
• finns is the present tense of finnas, meaning to exist / to be found

So:

• Det finns ett staket = There is a fence
• Det finns många hus här = There are many houses here

You would not normally use det är for this kind of idea.

Because staket is an ett-word in Swedish.

That affects two things:

1. The article is ett, not en
2. The adjective gets -t in the singular indefinite form

So:

• ett staket
• ett lågt staket

Compare with an en-word:

• en grind
• en låg grind

This is standard adjective agreement in Swedish.

No. In this word, -et is just part of the basic noun form.

• ett staket = a fence
• staketet = the fence

This can be confusing at first, because Swedish also uses endings like -et and -en to mark definiteness. But some nouns simply happen to end that way in their indefinite base form.

Here gården most likely means the yard or the courtyard.

The base word is gård, which can mean different things depending on context, such as:

• yard
• courtyard
• farm

In this sentence, yard/courtyard is the natural meaning.

It is definite because the sentence refers to a specific yard:

• gård = yard
• gården = the yard

The -en ending is the Swedish definite article attached to the noun.

Runt means around in a physical, spatial sense.

So runt gården means the fence goes around the yard.

It is a very natural choice here. You may also see kring or omkring, but runt is especially common in everyday Swedish for physical surroundings.

Because it refers to a specific gate, not just any gate.

Once the sentence has mentioned a fence around the yard, the gate is understood as the gate belonging to that fence or yard. Swedish often uses the definite form when the thing is identifiable from the situation.

• en grind = a gate
• grinden = the gate

So grinden sounds natural because the gate is already understood from the context.

Because öppen agrees with grinden, and grind is an en-word.

This adjective is used predicatively here, after är, but it still agrees with the noun:

• grinden är öppen = the gate is open
• fönstret är öppet = the window is open
• dörrarna är öppna = the doors are open

So:

• öppen for singular en-words
• öppet for singular ett-words
• öppna for plural

This is different from lågt earlier in the sentence, where the adjective comes before the noun: ett lågt staket.

Because adverbs of frequency such as alltid, ofta, nästan alltid, and ibland usually come after the finite verb in a main clause.

So:

• grinden är nästan alltid öppen
• hon kommer ofta hit
• de är alltid glada

That is the normal word order.

You can sometimes move the adverb for emphasis, but the sentence as given uses the most standard placement.

These mean different things.

• på eftermiddagen = in the afternoon / during the afternoon, often general or habitual
• i eftermiddag = this afternoon

In your sentence, på eftermiddagen fits because it describes what is usually true at that time of day.

Also, Swedish often uses the definite form of parts of the day in expressions like this:

• på morgonen
• på kvällen
• på natten
• på eftermiddagen

Because after och, Swedish starts a new main clause, and the normal order is still followed.

In the second clause, the subject comes first:

• grinden är nästan alltid öppen

That gives subject + verb.

Swedish is a V2 language, which means the finite verb is normally in the second position in a main clause. If something other than the subject came first, then you would get inversion:

• På eftermiddagen är grinden nästan alltid öppen

But in your sentence, the subject grinden comes first, so no inversion happens.

Not strictly.

In Swedish, a comma before och is often optional. Many writers would leave it out:

• Det finns ett lågt staket runt gården och grinden är nästan alltid öppen på eftermiddagen.

But using a comma is also acceptable here because the sentence joins two full clauses, and the comma can make it easier to read.

So the version with the comma is natural and correct.