Ich ziehe die Tischdecke glatt, bevor der Besuch kommt.

Because the verb here is really glattziehen, a separable verb meaning to smooth out / pull smooth.

In a main clause, separable verbs split:

• Ich ziehe die Tischdecke glatt.

In the infinitive or after a modal, they stay together:

• Ich will die Tischdecke glattziehen.
• Glattziehen takes a little effort.

So ziehe ... glatt is the normal split form.

Literally, it is something like to pull smooth.

With a Tischdecke (tablecloth), it means:

• to straighten it
• to smooth out wrinkles
• to pull it flat neatly on the table

So Ich ziehe die Tischdecke glatt is a natural way to say that someone is making the tablecloth look neat before company arrives.

Tischdecke is a feminine noun, so its basic article is die.

Here it is the direct object of ziehen, so it is in the accusative case. For feminine nouns, the article is still die in the accusative:

• nominative: die Tischdecke
• accusative: die Tischdecke

So even though it is an object, the form does not change.

Because glatt is not being used directly before a noun here.

Compare:

• die glatte Tischdecke = the smooth tablecloth
  → adjective before a noun, so it gets an ending

• Ich ziehe die Tischdecke glatt.
  → glatt describes the result of the action: I pull the tablecloth smooth / flat

So here glatt works more like a predicative/resultative adjective, not an attributive adjective, which is why there is no ending.

Because bevor introduces a subordinate clause, and in German subordinate clauses are normally separated from the main clause by a comma.

So:

• Ich ziehe die Tischdecke glatt, bevor der Besuch kommt.

This is standard German punctuation.

Because bevor is a subordinating conjunction. In German, subordinating conjunctions send the finite verb to the end of the clause.

So:

• bevor der Besuch kommt
• weil er müde ist
• dass sie heute arbeitet

This is one of the most important word-order patterns in German.

It can mean either, depending on context.

Besuch often refers to:

• a visit
• visitors / company / guests as a collective idea

In this sentence, it usually means something like:

• the guests
• the company
• the visitors

That is why the English translation is often less literal. German uses der Besuch where English would often say the guests or company.

Because Besuch is grammatically singular.

Even when it refers to more than one person, it is treated like a collective noun:

• Der Besuch kommt.

It is similar to using company in English:

• Company is coming.

So the verb is singular: kommt, not kommen.

Because German very often uses the present tense to talk about the future when the context makes the time clear.

Here, bevor already shows that the coming happens later:

• Ich ziehe die Tischdecke glatt, bevor der Besuch kommt.

German does this all the time:

• Morgen fahre ich nach Berlin.
• Nächste Woche kommt meine Schwester.

You do not need a special future tense unless you want extra emphasis or clarity.

Yes, absolutely.

• bevor der Besuch kommt sounds a bit more collective and idiomatic, like before the company arrives
• bevor die Gäste kommen is more direct and concrete: before the guests arrive

Both are natural, but they are not exactly identical in tone:

• der Besuch = the visit/company/visitors as a group or event
• die Gäste = the guests themselves

Because German main clauses normally follow the verb-second rule.

The first clause is:

• Ich | ziehe | die Tischdecke glatt

The conjugated verb ziehe must come in the second position.

If you move another element to the front, the verb still stays second:

• Vor dem Besuch ziehe ich die Tischdecke glatt.

That verb-second pattern is one of the basic rules of German sentence structure.