من تا حالا کفش سبز نخریده ام، اما خواهرم کفش سبز خریده است.

تا حالا means so far / up to now / until now.

A few useful notes:

• It is very common in everyday Persian.
• It often appears with the present perfect, just like English so far often does.
• A more formal alternative is تا کنون.

So in this sentence, تا حالا sets up the idea of at any time up to now.

They are present perfect forms.

• خریده است = has bought
• نخریده ام = have not bought

They are built like this:

• خریدن = to buy
• خریده = past participle, roughly bought
• then you add forms of to be:

Examples:

• خریده‌ام = I have bought
• خریده‌ای = you have bought
• خریده است = he/she/it has bought

For the negative, Persian adds نـ:

• نخریده‌ام = I have not bought

So the pattern is very similar to English have/has + bought, but Persian uses the participle plus personal endings/forms.

Because Persian is generally an SOV language: subject–object–verb.

So instead of English-style:

• I have not bought green shoes

Persian prefers:

• I green shoes have not bought

That is why you get:

• من ... کفش سبز نخریده‌ام
• خواهرم کفش سبز خریده است

Adverbs like تا حالا also usually come before the verb.

That is true: Persian often does omit subject pronouns because the verb ending already shows the person.

So you could say:

• تا حالا کفش سبز نخریده‌ام

and it would still clearly mean I have not bought green shoes so far.

Here, من is used mainly for contrast:

• I haven’t bought green shoes,
• but my sister has.

So the explicit من makes the contrast stronger and clearer.

Because -م is a possessive ending meaning my.

So:

• خواهر = sister
• خواهرم = my sister

This kind of ending attaches directly to nouns:

• کتابم = my book
• دوستم = my friend
• خواهرم = my sister

You can also say خواهرِ من, but خواهرم is usually more natural and compact.

Yes. There is an ezafe there in pronunciation:

• کفشِ سبز
• pronounced roughly kafsh-e sabz

Ezafe links a noun to what follows it, such as an adjective.

So Persian says:

• shoe green = green shoe / green shoes

Important point: after many consonants, the ezafe is not written, but it is still pronounced.

So although you see کفش سبز, you should read it as:

• کفشِ سبز

Because Persian does not have a true definite article like English the.

Also, indefinite meaning is often left unmarked if the context is clear.

So a bare noun like کفش سبز can mean something like:

• green shoes
• a green shoe
• the green shoes

depending on context.

Persian can mark indefiniteness in other ways, such as:

• یک = one / a
• sometimes -ی

But in a sentence like this, the bare noun phrase is completely natural.

Because را usually marks a specific or definite direct object.

Here, کفش سبز is being talked about in a more general / non-specific way, so را is not needed.

Compare:

• کفش سبز خریده‌ام = I have bought green shoes / a green shoe
• کفش سبز را خریده‌ام = I have bought the green shoes / that specific green shoe

So the absence of را tells you the object is not being treated as a specific known item.

This is a very common English-speaker question.

Persian does not always match English number marking exactly. A bare singular noun can sometimes be used where English would prefer a plural.

With کفش, Persian often uses the singular form in a broad or generic way, somewhat like footwear or a pair of shoes, depending on context.

If you want to make the plural explicit, you can say:

• کفش‌ها = shoes
• کفش‌های سبز = green shoes

But in many everyday sentences, bare کفش is perfectly natural.

Both mean but.

The main difference is tone/register:

• اما is a bit more formal or written
• ولی is very common in everyday speech

So this sentence uses a slightly more formal connector:

• اما

In casual conversation, many speakers would say:

• ولی

Both are correct.

Because these are treated a little differently in spelling.

• -ام in خریده‌ام is an attached ending, so it is normally written with a half-space: خریده‌ام
• است is usually written as a separate word: خریده است

So in careful modern spelling, you would usually write:

• نخریده‌ام
• خریده است

Many people type نخریده ام with a regular space, especially informally, but نخریده‌ام is the more standard spelling.

A more conversational version might be:

• تا حالا کفش سبز نخریدم، ولی خواهرم کفش سبز خریده.

A few spoken-style changes happened there:

• من is dropped because it is understood
• اما becomes ولی
• خریده است becomes خریده
• speakers often use نخریدم in conversation where formal written Persian might use نخریده‌ام

You may also hear something closer to the written form in speech:

• تا حالا کفش سبز نخریده‌م، ولی خواهرم کفش سبز خریده.

Both are natural, depending on the speaker and level of formality.