Můj podíl je malý, ale tato povinnost je důležitá.

Because můj has to agree with podíl in gender, number, and case.

Here, podíl is:

• masculine inanimate
• singular
• nominative (the subject form)

So the correct form is můj.

Compare:

• můj podíl = my share/part
• má povinnost = my duty
• mé město = my city

You may hear moje in colloquial Czech in some situations, but můj is the correct standard form here.

Tato means this, and it also has to agree with the noun it describes.

Povinnost is:

• feminine
• singular
• nominative

So the feminine singular nominative form of ten / this-that demonstrative is tato.

Compare:

• tento podíl = this share/part
• tato povinnost = this duty
• toto město = this city

Because Czech adjectives must agree with the noun they describe.

• podíl is masculine inanimate singular, so: malý
• povinnost is feminine singular, so: důležitá

So:

• malý podíl = a small share/part
• důležitá povinnost = an important duty

This kind of adjective agreement is one of the most important patterns in Czech grammar.

Both are in the nominative.

That is because they are the subjects of the two clauses:

• Můj podíl je malý
• tato povinnost je důležitá

In both clauses, the structure is basically:

subject + je + adjective

So the subject noun stays in the nominative.

Je means is. It is the 3rd person singular form of být = to be.

So:

• podíl je malý = the share is small
• povinnost je důležitá = the duty is important

It is the same verb in both clauses because both subjects are singular.

Normally, no. In a regular full sentence like this, you should keep je.

So:

• Můj podíl je malý is correct
• Můj podíl malý is not standard normal Czech

In headlines, notes, or very informal fragments, Czech may sometimes drop forms of to be, but learners should treat je as required here.

Because Czech does not have articles like English.

So Czech often leaves definiteness to:

• context
• word order
• demonstratives like tento / tato / toto

For example:

• povinnost can mean a duty or the duty, depending on context
• tato povinnost clearly means this duty

Yes. Ale means but and connects the two contrasting clauses:

• Můj podíl je malý
• ale tato povinnost je důležitá

It signals contrast: the speaker’s share is small, but the duty is still important.

Czech word order is more flexible than English, but not completely free.

This sentence has a very natural neutral order:

• Můj podíl je malý, ale tato povinnost je důležitá.

You could also say:

• Můj podíl je malý, tato povinnost je ale důležitá.

That still means basically the same thing, but the placement of ale changes the rhythm and emphasis a little.

For learners, the original version is an excellent neutral model.

They are related, but not exactly the same in style.

• tato = standard, careful, often written or formal-neutral
• ta = can mean that or sometimes work like the/that one in everyday speech
• tahle = more conversational, like this here / this one

So in a textbook-style sentence, tato povinnost is a very natural choice.

Because Czech noun gender is not determined only by the last letter.

Many feminine nouns do end in -a, but some feminine nouns end in a consonant, especially nouns ending in -ost, such as:

• radost = joy
• možnost = possibility
• povinnost = duty

So even though povinnost does not look like a typical -a feminine noun, it is still feminine, and that is why it takes:

• tato
• důležitá

Podíl is a masculine inanimate noun.

It can mean things like:

• share
• portion
• part
• sometimes stake
• sometimes contribution, depending on context

In this sentence, it likely means something like my share or my part in the matter.

Because it is masculine inanimate singular nominative, it matches:

• můj
• malý

Můj is pronounced approximately like mooy in English, but as one smooth syllable.

A few tips:

• ů here sounds like a long oo
• j in Czech sounds like English y

So můj is roughly mooy.

Not perfect English spelling, but close enough for a learner’s first approximation.

A rough guide is:

doo-leh-zhi-taa

Notes:

• dů = long doo
• ž sounds like the s in measure
• á is a long a

So the word has clear stress on the first syllable, as Czech normally does:

• DŮ-le-ži-tá

Because the sentence contains two full clauses, and each clause has its own predicate:

• Můj podíl je malý
• ale tato povinnost je důležitá

In English, you also normally repeat is here:

• My share is small, but this duty is important.

So Czech works very similarly in this case.