Гончар решил замесить глину.

Not necessarily. It is capitalized here because it is the first word in the sentence. In Russian, just like in English, the first word of a sentence gets a capital letter.

If you saw it in the middle of a sentence as a common noun, it would normally be гончар = potter.

It is in the nominative singular, because it is the subject of the sentence — the person doing the action.

The basic dictionary form is гончар.

Решил is the past tense masculine singular form of решить.

Russian past tense agrees with the subject in gender and number:

• он решил = he decided
• она решила = she decided
• они решили = they decided

Because гончар is grammatically masculine singular here, the verb becomes решил.

Because after решить Russian usually uses an infinitive to express what someone decided to do.

So:

• решил замесить = decided to knead / mix

This works very much like English decided to do something.

Замесить is a perfective verb, so it presents the action as a single complete task with a result.

In this sentence, the idea is that the potter decided to knead/mix the clay properly as a complete action, not just engage in the process in a general way.

A rough contrast is:

• месить = to be kneading, to knead in process
• замесить = to knead/mix up completely, to prepare by kneading

Russian often prefers the perfective infinitive after решил when talking about a one-time intended action.

Because глину is in the accusative case, not the nominative.

Here глина is the direct object of the verb замесить — it is what the potter decided to knead.

For many feminine nouns ending in -а, the singular accusative ends in -у:

• глина = clay
• глину = clay (as a direct object)

There are two nouns here:

• Гончар — nominative singular: the subject
• глину — accusative singular: the direct object

So the structure is:

[subject] + [past-tense verb] + [infinitive] + [object]

Not by itself. Решил tells us that the decision happened in the past. The infinitive замесить tells us what he decided to do.

So the sentence means that the potter decided to knead the clay. It does not automatically prove that he actually carried it out, unless the wider context says so.

The given order is very natural and neutral:

Гончар решил замесить глину.

That is a straightforward subject + verb + infinitive + object order.

Russian word order is flexible, so other orders are possible for emphasis, for example:

• Глину гончар решил замесить.

But the original version is the most neutral and textbook-like.

Because Russian has no articles.

So Гончар can mean:

• the potter
• a potter

And глину can mean:

• the clay
• some clay

Context tells you which one is meant.

The stress is:

гонча́р реши́л замеси́ть гли́ну

A rough pronunciation guide could be:

gan-CHAR rye-SHEEL za-mye-SEET GLEE-noo

The most important thing for a learner is to notice the stressed syllables, because Russian stress is not always predictable.