W czasie lekcji mój zeszyt i piórnik leżą na ławce.

W czasie lekcji is a fixed and very common way to say during the lesson.

• w takes the locative here, so czas becomes czasie
• lekcji is in the genitive singular, because the phrase is literally structured like in the time of the lesson

So the grammar is:

• w czasie = during / in the course of
• lekcji = of the lesson

This is a useful pattern:

• w czasie obiadu = during lunch
• w czasie wakacji = during the holidays
• w czasie spotkania = during the meeting

Yes. Podczas lekcji is also correct and very natural.

Both mean during the lesson, but there is a small stylistic difference:

• podczas lekcji is a bit more compact and often feels slightly more formal or neutral
• w czasie lekcji is also very common and natural, and may feel a little more expanded

So these are both fine:

• Podczas lekcji mój zeszyt i piórnik leżą na ławce.
• W czasie lekcji mój zeszyt i piórnik leżą na ławce.

Because zeszyt is a masculine singular noun, and the possessive adjective must agree with it.

So:

• mój = masculine singular
• moja = feminine singular
• moje = neuter singular, or non-masculine-personal plural in some contexts

Since zeszyt is masculine:

• mój zeszyt = my notebook

Compare:

• moja książka = my book
• moje krzesło = my chair

In Polish, just like in English, one possessive can often cover two coordinated nouns.

So:

• mój zeszyt i piórnik means my notebook and pencil case

It is understood that both are yours.

You could also repeat the possessive for emphasis or clarity:

• mój zeszyt i mój piórnik

But in normal speech, using mój only once is perfectly natural.

Because the subject is actually two things:

• mój zeszyt
• piórnik

Together they form a compound subject, so the verb must be plural.

That is why:

• leży = lies / is lying for one thing
• leżą = lie / are lying for more than one thing

Compare:

• Mój zeszyt leży na ławce. = My notebook is lying on the desk.
• Mój zeszyt i piórnik leżą na ławce. = My notebook and pencil case are lying on the desk.

Polish often prefers more specific verbs for physical position.

So instead of saying only that something is somewhere, Polish often says whether it:

• lies = leży / leżą
• stands = stoi / stoją
• hangs = wisi / wiszą

For objects like a notebook and a pencil case, leżeć is natural because they are resting horizontally on a surface.

Examples:

• Książka leży na stole. = The book is on the table.
• Butelka stoi na stole. = The bottle is on the table.
• Obraz wisi na ścianie. = The picture is on the wall.

English often just says is, but Polish usually chooses the position verb.

Ławce is locative singular.

That is because na can take different cases depending on meaning:

• na + locative = location, when something is already somewhere
• na + accusative = movement onto a surface

Here we are talking about location, not motion:

• leżą na ławce = they are lying on the desk

So:

• na ławce = on the desk/bench

Compare:

• Kładę zeszyt na ławkę. = I put the notebook onto the desk.
  Here ławkę is accusative because there is movement.

Because na is used for being on a surface, while w means inside something.

A notebook and pencil case are typically on top of a school desk/bench, so:

• na ławce = on the desk

If something were inside a drawer, bag, or box, you would use w:

• w plecaku = in the backpack
• w szufladzie = in the drawer

So the choice depends on the physical relationship:

• na = on
• w = in

Yes, ławka can be a little tricky.

It often means:

• bench
• but in a school context it commonly refers to a school desk or school bench

So in a sentence about a lesson, notebook, and pencil case, ławka is naturally understood as a school desk.

Context matters a lot:

• ławka w parku = a bench in the park
• ławka w klasie = a desk / school bench in the classroom

The dictionary form is leżeć, meaning to lie.

Leżą is the 3rd person plural present tense form.

Present tense forms:

• leżę = I lie / am lying
• leżysz = you lie
• leży = he/she/it lies
• leżymy = we lie
• leżycie = you all lie
• leżą = they lie

In this sentence, the subject is plural, so we use leżą.

Yes, Polish word order is more flexible than English word order.

The version:

• W czasie lekcji mój zeszyt i piórnik leżą na ławce.

is neutral and natural.

But other orders are also possible, with different emphasis:

• Mój zeszyt i piórnik leżą na ławce w czasie lekcji.
• Na ławce leżą mój zeszyt i piórnik.
• Mój zeszyt i piórnik na ławce leżą.
  This last one is much more marked or poetic, not the normal neutral order.

Very roughly:

• what comes earlier can sound more topical or already known
• what comes later can sound more new or emphasized

Yes, if the context already makes it clear whose they are.

So:

• Zeszyt i piórnik leżą na ławce. = The notebook and pencil case are lying on the desk.

This is perfectly grammatical. Adding mój simply makes it explicit that they are yours.

Polish often omits possessives when the owner is obvious from context, but keeping mój is also completely normal.

Polish does not have articles like English a/an and the.

That means nouns like zeszyt, piórnik, and ławka appear without articles.

Whether something is understood as:

• a notebook
• the notebook
• my notebook

depends on:

• context
• word order
• possessives like mój
• the broader situation

So ławce by itself can mean a desk, the desk, or just desk depending on context.

Yes. Piórnik is a masculine inanimate noun.

That is why in the singular you would say:

• piórnik leży = the pencil case is lying

And if you used a possessive directly with it:

• mój piórnik = my pencil case

So both zeszyt and piórnik are masculine singular nouns, which helps explain why mój fits naturally before the first noun.

It can do either, depending on context.

The present tense in Polish, like in English, can describe:

• a current situation
• a general fact
• a habitual situation

So this sentence could mean:

• right now during the lesson, my notebook and pencil case are on the desk
• as a general classroom habit, during lessons my notebook and pencil case are on the desk

Without more context, both readings are possible.