Vstup je zdarma, takže přijde hodně lidí.

Here vstup means entry/admission, not the doorway itself.

• vstup = entry, admission, access
• vchod = entrance, doorway, way in

So Vstup je zdarma means Admission is free or Entry is free, not The entrance is free in the physical sense.

Zdarma means for free / free of charge.

In this sentence, it behaves like a fixed predicate expression after je. It does not change its form for gender, number, or case.

So:

• Vstup je zdarma. = Admission is free.
• Káva je zdarma. = The coffee is free.
• Tyto služby jsou zdarma. = These services are free.

Even though English uses an adjective (free), Czech uses zdarma as an indeclinable word.

Yes. Zdarma and zadarmo both mean for free.

Very roughly:

• zdarma = a bit more neutral or formal
• zadarmo = common and conversational

So both of these are possible:

• Vstup je zdarma.
• Vstup je zadarmo.

A learner will most often see zdarma in signs, ads, and standard written language.

Takže means so, therefore, or as a result. It introduces a consequence.

• Vstup je zdarma, takže přijde hodně lidí. = Admission is free, so a lot of people will come.

Do not confuse it with protože, which means because and introduces a reason.

Compare:

• Vstup je zdarma, takže přijde hodně lidí. = Admission is free, so a lot of people will come.
• Přijde hodně lidí, protože vstup je zdarma. = A lot of people will come because admission is free.

This is a very common Czech point: přijde is the present form of a perfective verb, but perfective present forms usually refer to the future.

The verb here is přijít = to come / to arrive in a completed sense.

So:

• přijde = will come / will arrive

This is normal in Czech:

• zítra přijdu = I will come tomorrow
• on přijde později = he will come later

If you want a more ongoing or repeated sense, Czech uses an imperfective verb instead, such as přicházet.

Because hodně requires the genitive plural.

The basic noun is:

• lidé = people (nominative plural)

But after hodně, Czech uses:

• hodně lidí = a lot of people

This is very common with quantity words:

• hodně lidí = a lot of people
• málo času = little time
• moc práce = a lot of work

So lidí here is the correct form after hodně.

Grammatically, Czech often treats expressions like hodně lidí as a quantified unit, so the verb is commonly in the 3rd person singular.

That is why you get:

• Přijde hodně lidí.
• Přišlo hodně lidí.

This may feel strange to an English speaker, because English agrees with people and uses a plural verb. Czech often agrees with the quantity expression as a whole instead.

So even though the meaning is plural, the verb form is typically singular.

In standard Czech, lidí is the correct genitive plural form of lidé.

• lidé = people
• lidí = of people / people after quantity words like hodně

The form lidi is very common in everyday speech, but in this sentence the standard form is lidí because it follows hodně.

So:

• standard: hodně lidí
• colloquial speech: you may hear hodně lidí anyway; lidi is more relevant in other positions, like Ti lidi... in colloquial Czech

Yes, that is also possible.

Both are natural:

• takže přijde hodně lidí
• takže hodně lidí přijde

The difference is mostly about information focus.

• přijde hodně lidí puts the new/important information naturally at the end: a lot of people
• hodně lidí přijde can put a bit more emphasis on hodně lidí as the topic or contrast

In many contexts, both are fine. Czech word order is more flexible than English, but it often reflects emphasis rather than changing the basic meaning.

Yes. On signs, posters, and advertisements, Czech often drops je.

So you will often see:

• Vstup zdarma = Free admission

That is a short headline-style expression. In a full normal sentence, Vstup je zdarma is the complete form.