यह कहानी छोटी है, लेकिन बहुत अच्छी है।

यह means this.

In careful transliteration, it is often written yah, but in everyday speech it is usually pronounced more like yeh, and sometimes even ye. So यह कहानी means this story.

A useful comparison:

• यह = this
• वह = that

Hindi normally does not use articles the way English does.

So कहानी can mean:

• a story
• the story
• just story

The context tells you which one is meant. In this sentence, यह already makes it specific, so यह कहानी is clearly this story.

In Hindi, every noun has a grammatical gender, usually either masculine or feminine. कहानी is a feminine noun.

This is grammatical gender, not biological sex. A story is not literally female; it is just treated as feminine in the grammar. Because of that, words that describe कहानी often have to match its gender.

Because कहानी is feminine singular, the adjectives must match it.

The basic masculine singular forms are:

• छोटा = small / short
• अच्छा = good

With a feminine singular noun, they become:

• छोटी
• अच्छी

So:

• छोटा लड़का = a short/small boy
• छोटी कहानी = a short story

Because here they are being used as predicate adjectives, not as adjectives directly attached before the noun.

Compare these two patterns:

• छोटी कहानी = a short story
• कहानी छोटी है = the story is short

So in this sentence, Hindi is using the X is Y pattern:

• यह कहानी छोटी है = This story is short

The same thing happens in the second half:

• [यह कहानी] बहुत अच्छी है = [This story] is very good

It can mean either, depending on context.

With something like a story, speech, or movie, it usually means short or brief.

So here:

• कहानी छोटी है means the story is short, not usually the story is small

Context decides the most natural meaning.

Because the sentence has two separate clauses joined by लेकिन:

• यह कहानी छोटी है
• लेकिन बहुत अच्छी है

Each clause has its own is, so Hindi normally uses है in both parts.

English sometimes avoids repetition more freely, but standard Hindi usually keeps the verb in each clause.

Because it is already understood from the first clause.

The full version could be:

• यह कहानी छोटी है, लेकिन यह कहानी बहुत अच्छी है।

But that sounds repetitive, so Hindi naturally leaves the subject out the second time when it is obvious.

This is very common in Hindi. If the subject is clear, it is often omitted.

In the present tense, है does not show gender. It mainly changes for number and person.

So:

• वह अच्छा है = he/it is good
• वह अच्छी है = she/it is good

Notice that अच्छा / अच्छी changes, but है stays the same.

So the gender is shown by the adjective here, not by है.

बहुत means very here.

It comes before the adjective it modifies:

• बहुत अच्छी = very good

A few examples:

• बहुत अच्छा = very good
• बहुत बड़ी = very big
• बहुत जल्दी = very quickly / very soon

बहुत does not change form for gender or number.

लेकिन means but.

It joins two contrasting ideas:

• यह कहानी छोटी है = This story is short
• लेकिन बहुत अच्छी है = but it is very good

So लेकिन sits between the two clauses, just like but in English.

A common shorter spoken alternative is पर, but लेकिन is perfectly natural and standard.

Yes, but it means something slightly different in structure.

• यह कहानी छोटी है = This story is short
• यह छोटी कहानी है = This is a short story

Both can translate naturally into English, but the grammar is different:

• कहानी छोटी है → the noun comes first, then the description
• छोटी कहानी → the adjective directly modifies the noun

So your original sentence focuses on the story being short, while यह छोटी कहानी है presents it more as this is a short story.