Ĉi tie mi aĉetas pomojn, sed tie mia amiko aĉetas bananojn.

Tie means there.

Adding ĉi makes it more specific and closer to the speaker:

• tie = there
• ĉi tie = here

In Esperanto, ĉi is often used with place words from the ti- series:

• tio = that
• ĉi tio = this
• tie = there
• ĉi tie = here

So ĉi tie mi aĉetas pomojn literally feels like here I buy apples.

Esperanto word order is fairly flexible. The most neutral order is often:

• subject + verb + object

So you could also say:

• Mi aĉetas pomojn ĉi tie.

But putting ĉi tie first emphasizes location:

• Ĉi tie mi aĉetas pomojn = Here, I buy apples
• Tie mia amiko aĉetas bananojn = There, my friend buys bananas

So the sentence starts with the place to highlight the contrast between here and there.

Mi means I.

Mia means my. It is the possessive form related to mi:

• mi = I
• mia = my

So:

• mi aĉetas = I buy
• mia amiko aĉetas = my friend buys

In mia amiko, the word mia describes amiko, so it works like an adjective.

In Esperanto, words ending in -a are adjective-like words. Possessives behave this way too.

So:

• bona = good
• ruĝa = red
• mia = my

Because mia is adjective-like, it modifies a noun:

• mia amiko = my friend
• mia libro = my book

If needed, it also agrees with the noun in plural and accusative:

• miaj amikoj = my friends
• miajn amikojn = my friends (as direct object)

The ending -as marks the present tense in Esperanto.

So:

• aĉeti = to buy
• aĉetas = buy / am buying / does buy / is buying

In Esperanto, the present tense can cover several English present-time meanings, depending on context.

Other common verb endings are:

• -is = past
• -os = future
• -us = conditional
• -u = command or jussive
• -i = infinitive

So mi aĉetas means I buy or I am buying, depending on context.

They have two endings added:

• -o = noun
• -j = plural
• -n = accusative, marking the direct object

So:

• pomo = apple
• pomoj = apples
• pomojn = apples as the direct object

And:

• banano = banana
• bananoj = bananas
• bananojn = bananas as the direct object

Since these are the things being bought, they are direct objects, so they take -n.

Esperanto uses the accusative ending -n to show which noun is the direct object of the verb.

In this sentence:

• mi aĉetas pomojn = I buy apples
• mia amiko aĉetas bananojn = my friend buys bananas

The -n tells you what is being bought.

This helps make the sentence clear even when word order changes. For example:

• Pomojn mi aĉetas ĉi tie. still means
• Apples I buy here.

Because pomojn has -n, you know it is the object, not the subject.

Esperanto does not require an article in many cases where English does.

It does have a definite article:

• la = the

But there is no indefinite article like English a or an.

So:

• Mi aĉetas pomojn can mean I buy apples, I am buying apples, or sometimes I buy some apples, depending on context.

You would only add la if you mean specific apples already known in context:

• Mi aĉetas la pomojn = I am buying the apples

Sed means but.

It connects the two parts of the sentence and shows contrast:

• Ĉi tie mi aĉetas pomojn
• sed
• tie mia amiko aĉetas bananojn

The contrast is between:

• ĉi tie and tie
• mi and mia amiko
• pomojn and bananojn

So sed is a very natural choice here.

Yes. That would also be correct.

Esperanto allows fairly flexible word order, and you can switch the two clauses:

• Ĉi tie mi aĉetas pomojn, sed tie mia amiko aĉetas bananojn.
• Tie mia amiko aĉetas bananojn, sed ĉi tie mi aĉetas pomojn.

The difference is mainly about emphasis and what you want to mention first.

The letter ĉ is pronounced like ch in church.

So:

• ĉi sounds roughly like chee
• aĉetas sounds roughly like ah-CHEH-tas

A few helpful pronunciation points from this sentence:

• c would be like ts, but here we have ĉ, not c
• j in Esperanto sounds like English y
• stress usually falls on the second-to-last syllable

So:

• aĉetas → a-ĈE-tas
• bananojn → ba-na-NOJN

Amiko is traditionally the masculine form, and amikino is specifically a female friend.

However, in actual use, some speakers use amiko more generally when sex is irrelevant or unknown, while others prefer newer gender-neutral solutions in modern Esperanto.

For a beginner, the key thing is:

• amiko = friend
• amikino = female friend

In this sentence, mia amiko is best understood simply as my friend unless the context makes gender important.

Yes, that is also grammatical.

Placing ĉi tie and tie at the end sounds a bit more neutral in some contexts:

• Mi aĉetas pomojn ĉi tie, sed mia amiko aĉetas bananojn tie.

The original sentence puts the location first to emphasize the contrast between here and there. Your version keeps the same meaning but shifts the focus slightly.