Najpierw otwórz ul, następnie sprawdź ramkę pszczelarską.

Because this sentence gives commands. Otwórz and sprawdź are imperative forms, meaning open! and check!

The dictionary forms are:

• otworzyć = to open
• sprawdzić = to check

In this sentence, the speaker is telling one person what to do, so Polish uses the singular informal imperative:

• otwórz
• sprawdź

It is informal singular, so it is directed at one person in a direct way, like English Open the hive, then check the frame.

If you wanted to be more formal in Polish, you would usually not use this bare imperative with Pan/Pani. Instead, Polish often uses a structure like:

• Niech pan otworzy ul
• Niech pani sprawdzi ramkę pszczelarską

If you were speaking to more than one person, you would use plural imperative forms:

• otwórzcie
• sprawdźcie

Polish usually does not need subject pronouns when the verb form already shows who the subject is.

In English, you must say:

• Open the hive

But in Polish, the imperative ending already tells you it is a command to you, so ty is normally omitted:

• Otwórz ul

Adding ty is possible, but it would usually sound marked or emphatic.

Both words organize the sequence of actions.

• najpierw = first
• następnie = next / then / subsequently

So the sentence means:

• first do action 1
• then do action 2

They are very natural in instructions. Najpierw often introduces the first step, and następnie sounds slightly more formal or instructional than everyday potem.

For example:

• Najpierw otwórz ul, potem sprawdź ramkę pszczelarską.

That would also be correct, but następnie fits well in procedural language.

Because ul is a masculine inanimate noun, and in the singular, masculine inanimate nouns often have the same form in the nominative and accusative.

Here, ul is the direct object of otwórz, so it is in the accusative case. But its accusative form happens to look exactly the same as the nominative:

• nominative: ul
• accusative: ul

So the form does change in grammar, but not in appearance.

Because ramkę is the accusative singular form, and the noun is the direct object of sprawdź.

The base form is:

• ramka = frame

But after a verb like sprawdzić, the direct object usually goes into the accusative:

• nominative: ramka
• accusative: ramkę

This is very common with feminine nouns ending in -a:

• książka → książkę
• lampa → lampę
• ramka → ramkę

Because the adjective must agree with the noun it describes.

The noun here is ramkę, which is:

• feminine
• singular
• accusative

So the adjective must also be:

• feminine
• singular
• accusative

That is why you get:

• ramka pszczelarska in the dictionary/basic form
• ramkę pszczelarską in this sentence

This is adjective-noun agreement in Polish.

Yes, that is also grammatically correct.

In Polish, adjectives often come before the noun:

• pszczelarską ramkę

But they can also come after the noun:

• ramkę pszczelarską

The version with the adjective after the noun can sound a bit more technical, descriptive, or stylistically specific in some contexts. In instructional or specialized language, that order is not unusual.

So both are possible:

• sprawdź ramkę pszczelarską
• sprawdź pszczelarską ramkę

Both verbs are perfective:

• otworzyć → otwórz
• sprawdzić → sprawdź

Perfective verbs focus on a completed action, which is very natural in step-by-step instructions:

• open the hive
• check the frame

The idea is to complete each action once.

If you used imperfective verbs instead, the meaning would shift more toward process, repetition, or ongoing activity. For example:

• otwieraj
• sprawdzaj

Those would sound more like:

• keep opening / be opening
• keep checking / check repeatedly

So in a one-time instruction, the perfective imperative is the normal choice.

The comma is natural and correct because the sentence contains two coordinated command clauses:

• Najpierw otwórz ul
• następnie sprawdź ramkę pszczelarską

The comma helps separate the two steps clearly. In instructional writing, this kind of punctuation is very common.

So:

• Najpierw otwórz ul, następnie sprawdź ramkę pszczelarską.

looks clear and natural.