La entreprenisto izolos la ĉambron.

In Esperanto, the verb ending shows the tense.

• -as = present
• -is = past
• -os = future
• -us = conditional
• -u = command / wish
• -i = infinitive

So:

• izoli = to isolate / to insulate
• izolas = isolates / is isolating
• izolis = isolated
• izolos = will isolate / will insulate

Esperanto usually does not need a separate word like will. The ending -os already gives that meaning.

The -n marks the direct object.

In this sentence, la ĉambron is the thing being affected by the action. The entrepreneur/contractor is doing something to the room, so ĉambro becomes ĉambron.

• La entreprenisto = the entrepreneur / contractor
• izolos = will isolate / will insulate
• la ĉambron = the room as the object of the verb

This -n ending is called the accusative ending.

Because la entreprenisto is the subject, not the object.

The subject is the person or thing doing the action.
The object is the person or thing receiving the action.

Here:

• La entreprenisto = the one doing the action
• la ĉambron = the thing receiving the action

Only the direct object gets -n here.

It can be broken down into parts:

• entrepren- = undertake / take on
• -ist- = a person associated with an activity, profession, or practice
• -o = noun ending

So entreprenisto literally means something like a person who undertakes things. Depending on context, it can mean entrepreneur, businessperson, or sometimes contractor.

A native English speaker may notice that the best translation depends on context more than the Esperanto form itself.

La is the Esperanto definite article, meaning the.

So:

• la entreprenisto = the entrepreneur / the contractor
• la ĉambron = the room

Esperanto uses only one article: la.
There is no separate word for a or an.

So:

• entreprenisto = an entrepreneur / entrepreneur
• la entreprenisto = the entrepreneur

Because Esperanto simply does not have an indefinite article.

English distinguishes:

• a room
• the room

Esperanto distinguishes only by using or not using la:

• ĉambro = a room / room
• la ĉambro = the room

So the absence of la often corresponds to English a/an, but Esperanto does not require a separate word for it.

Yes, to some extent.

Because ĉambron has the accusative ending -n, Esperanto allows more flexible word order than English. For example, these mean basically the same thing:

• La entreprenisto izolos la ĉambron.
• La ĉambron izolos la entreprenisto.

The -n tells you that ĉambron is the object, even if it comes earlier.

That said, the normal and clearest order is usually:

subject + verb + object

So the original sentence is the most straightforward version.

Ĉ is pronounced like ch in chair.

So:

• ĉambro sounds roughly like CHAHM-bro
• ĉambron adds the object ending -n

A few helpful pronunciation points:

• ĉ = ch as in church
• o is a pure vowel, like o in many European languages, not the diphthong English often uses
• the stress in Esperanto is usually on the second-to-last syllable

So ĉambron is stressed like CHAM-bron.

The dictionary forms are:

• entreprenisto = entrepreneur / contractor
• izoli = to isolate / to insulate
• ĉambro = room

In Esperanto, dictionary forms usually look like this:

• nouns end in -o
• adjectives end in -a
• adverbs end in -e
• verbs are listed in the infinitive ending -i

So in the sentence:

• izolos comes from izoli
• ĉambron comes from ĉambro

Not always in the narrow English sense.

Depending on context, izoli can mean:

• to isolate
• to insulate
• to separate from outside influence/contact

In a sentence about a room, many learners may expect insulate as the natural English translation, even though the Esperanto verb is built from the same idea as isolate.

So the exact English choice depends on context.

Only the verb ending would change:

• La entreprenisto izolas la ĉambron. = The entrepreneur/contractor isolates / is insulating the room.
• La entreprenisto izolis la ĉambron. = The entrepreneur/contractor isolated the room.
• La entreprenisto izolos la ĉambron. = The entrepreneur/contractor will isolate / will insulate the room.

This is one of the nicest features of Esperanto: tense changes are very regular.