A medida que llega más gente, es más difícil encontrar sitio en el teatro.

A medida que means as / as more..., as, or in proportion as. It introduces a gradual change that happens at the same time as something else.

So in this sentence, the idea is:

• A medida que llega más gente... = As more people arrive...
• ..., es más difícil encontrar sitio... = ..., it becomes harder to find a place/seat...

It is a very common structure for describing things that change progressively.

Because gente is grammatically singular in Spanish, even though it refers to many people.

So Spanish treats it like:

• la gente llega
• mucha gente llega
• más gente llega

not:

• la gente llegan
• más gente llegan

This is one of the most common things English speakers notice, because English often thinks of people as plural, but Spanish gente is a singular collective noun.

Gente means people in a general, collective sense. It is singular in grammar but plural in meaning.

Compare:

• gente = people, folks, a crowd, people in general
• personas = persons/people as individual countable units

So:

• Llega más gente = More people are arriving
• Llegan más personas = also possible, but a bit more neutral or literal

In everyday Spanish, gente is extremely common.

This is a very common Spanish pattern:

• es + adjective + infinitive

Here:

• es = it is
• más difícil = more difficult
• encontrar sitio = to find a place/seat

So es más difícil encontrar sitio literally means:

• it is more difficult to find a place

Spanish often uses this structure where English uses it is + adjective + to + verb.

Examples:

• Es fácil entenderlo = It is easy to understand it
• Es imposible entrar = It is impossible to get in
• Es más difícil encontrar sitio = It is harder to find space/a seat

Because Spanish often does not need a dummy subject like English it.

English says:

• It is difficult
• It is raining

Spanish usually just says:

• Es difícil
• Llueve

So es más difícil encontrar sitio already means it is more difficult to find a place, even though Spanish does not include a separate word for it.

In Spanish, it is very normal to omit the article in expressions like this when you mean any available place/space, not one specific place.

So:

• encontrar sitio = to find space / to find somewhere to sit / to find room
• encontrar un sitio = to find a place

Both are possible, but encontrar sitio sounds very natural and idiomatic when talking about availability.

It is similar to other Spanish expressions like:

• No hay sitio = There’s no room
• ¿Queda sitio? = Is there any space left?

Here sitio means something like space, room, or a place to sit. In the context of a theatre, it often implies an available seat/place.

In Spain, sitio is very natural in this kind of sentence.

Related words:

• sitio = place/space/room
• asiento = seat (more specifically the physical seat)
• lugar = place, spot, position

So in a theatre:

• encontrar sitio = find room / find a place / find a seat
• encontrar un asiento = find a seat

Sitio is a bit broader and very idiomatic here.

Because en marks location, while a often marks movement toward a destination.

• en el teatro = in the theatre / at the theatre
• al teatro = to the theatre

This sentence is talking about where it is hard to find space, so it needs the location:

• en el teatro

If you said al teatro, it would sound like movement toward the theatre, which is not the meaning here.

Because the two más do different jobs:

1. más gente = more people
   Here más modifies the noun gente.

2. más difícil = more difficult / harder
   Here más makes a comparison with the adjective difícil.

So the sentence expresses a parallel increase:

• more people arrive
• it becomes harder

This kind of double comparative idea is very common.

Normally, in a sentence like this, it takes the indicative because it describes a real, ongoing process:

• A medida que llega más gente...

The speaker is presenting this as an actual fact: as more people arrive, it gets harder.

So the indicative is the natural choice here.

Yes, Spanish can change word order for emphasis, but es más difícil encontrar sitio is the most neutral and natural order here.

Possible variant:

• A medida que llega más gente, más difícil es encontrar sitio en el teatro.

That version is understandable, but it sounds a bit more literary or emphatic. For everyday use, the original sentence is more standard.

Yes. That would also be correct:

• A medida que llegan más personas, es más difícil encontrar sitio en el teatro.

The difference is mainly this:

• más gente = more idiomatic, more common in everyday speech
• más personas = also correct, slightly more explicit or neutral

Notice that with personas, the verb becomes plural:

• llegan más personas

because personas is a plural noun.

Yes, especially because of sitio in this context. In Spain, sitio is very common for room/space/place.

In other Spanish-speaking areas, people might also say:

• encontrar lugar
• encontrar asiento

But the original sentence sounds very natural in Spain:

• A medida que llega más gente, es más difícil encontrar sitio en el teatro.