Ianitor ante portam urbis sedet et viatores interrogat.

Ianitor is nominative singular because it is the subject of both verbs: sedet (sits) and interrogat (questions/asks). Latin often keeps the same subject for multiple verbs joined by et, unless a new subject is introduced.

Ante is a preposition that takes the accusative to mean in front of/before (in a physical sense).

• portam is accusative singular of porta (gate) because it is the object of ante.
• urbis is genitive singular of urbs (city) showing possession: the gate of the city.

So ante portam urbis = in front of the city’s gate.

Latin commonly expresses “X of Y” with the genitive: porta urbis = gate of the city.
You could express a similar idea with an adjective (porta urbana), but that tends to mean something like an urban/city-type gate rather than clearly the city’s gate. The genitive is the straightforward “belongs to / associated with” construction.

Context and the kind of noun after it help. Ante can mean:

• before (time): ante bellum = before the war
• in front of (place): ante ianuam = in front of the door

Here portam (gate) is a physical location, so ante portam is naturally in front of the gate.

Both are present tense, 3rd person singular:

• sedet = he/she sits / is sitting
• interrogat = he/she questions / is questioning

Latin doesn’t use a separate verb like English do/does for simple present questions or emphasis, and it often doesn’t need is as an auxiliary for the continuous idea—context supplies whether you read it as sits or is sitting.

Latin verbs usually encode the subject in their endings. The -t in sedet and interrogat marks 3rd person singular, so an explicit pronoun (is/ea) is unnecessary unless you want emphasis or contrast.

Viatores is accusative plural (same form as nominative plural for this noun), functioning as the direct object of interrogat: the gatekeeper questions the travelers.

You can tell it’s accusative by its job in the sentence: interrogat is a transitive verb here, and the people being questioned are the object.

Yes, very often. Interrogare commonly takes a direct object in the accusative for the person questioned:

• viatorem interrogat = he questions a traveler

It can also take an object that represents the thing asked (often as an indirect construction or with an embedded question), but in your sentence it’s the straightforward “question someone.”

Latin word order is flexible because endings show grammatical roles. A common neutral pattern is:

• subject early (Ianitor)
• important location phrase placed early (ante portam urbis)
• verbs often later (sedet … interrogat)

Also, having ante portam urbis near the start sets the scene before stating the actions.

Here et is the ordinary coordinating conjunction and, joining two verb phrases that share the same subject:

• (Ianitor) sedet and (Ianitor) interrogat

It can sometimes mean also/even, but in this structure it’s best read as plain and.

Urbs can mean city, and in some contexts it can also refer to the City (especially Rome). Without extra context, urbis is simply of the city—a generic city.

You would typically use ad + accusative for to/at (near), or another construction depending on nuance:

• ad portam urbis sedet = he sits at/by the city gate (near it)
• in porta would suggest in/on the gate (usually not what you want)

So the main change is swapping ante for ad (and keeping portam accusative).