Tolgo i piselli dal congelatore e li lascio scongelare sul tavolo.

In Italian, the subject pronoun is often omitted because the verb ending already shows who is doing the action.

• tolgo = I take out / I remove
• lascio = I leave / I let

So Italian does not need io here, although you could say Io tolgo i piselli... if you wanted extra emphasis.

Italian often uses the present tense in situations where English might also use the present, especially for:

• describing a routine
• giving instructions
• narrating steps in a process, such as in a recipe

So Tolgo i piselli dal congelatore e li lascio scongelare sul tavolo can sound like:

• I take the peas out of the freezer and leave them to thaw on the table
• or, in a recipe/instruction style, Take the peas out of the freezer and leave them to thaw on the table

Italian commonly uses the present for this kind of step-by-step action.

Italian uses articles more often than English. So where English might say peas, Italian often says the peas:

• i piselli = the peas

This does not always sound as definite in Italian as it does in English. In many everyday contexts, the article is simply the normal way to refer to a noun.

Also, piselli is masculine plural, so the article is i.

Togliere has a broad meaning: to remove, to take away, to take off, or in this context to take out.

So Tolgo i piselli dal congelatore literally means:

• I remove the peas from the freezer

In natural English, we would usually say:

• I take the peas out of the freezer

Italian often uses togliere where English prefers take out.

Dal is a contraction of:

• da = from
• il = the

So:

• dal congelatore = from the freezer

This kind of contraction is very common in Italian:

• da + il = dal
• a + il = al
• di + il = del
• in + il = nel
• su + il = sul

Li is a direct object pronoun meaning them, referring to i piselli.

So:

• i piselli = the peas
• li = them

Instead of repeating the noun, Italian uses the pronoun:

• Tolgo i piselli dal congelatore e li lascio scongelare...
• I take the peas out of the freezer and leave them to thaw...

Because piselli is masculine plural, the pronoun is li.

In Italian, object pronouns usually go before the conjugated verb.

So you get:

• li lascio = I leave them
• not lascio li

This is a basic word-order rule with unstressed object pronouns in Italian.

Compare:

• Lo vedo = I see him/it
• La prendo = I take it
• Li lascio = I leave them

This is a very common Italian structure:

• lasciare + object + infinitive

It means to let or to leave someone/something to do something.

So:

• li lascio scongelare

literally means:

• I leave them to thaw
• or I let them thaw

Here:

• li = them
• lascio = I leave / I let
• scongelare = to thaw / to defrost

This is similar to:

• Lo lascio parlare = I let him speak
• La lascio riposare = I leave it to rest

Because the meaning is different.

• li scongelo = I thaw them / I defrost them
• li lascio scongelare = I leave them to thaw

The first suggests that you are actively defrosting them, perhaps using a microwave or another method.
The second suggests that you simply put them somewhere and let the thawing happen naturally.

So in this sentence, lascio scongelare fits the idea of leaving the peas on the table until they thaw.

Yes, that is possible, but it is a slightly different wording.

• li lascio scongelare = I leave them to thaw
• li lascio scongelarsi = I leave them to thaw themselves / to get thawed

In everyday speech, lasciare + infinitive without the reflexive pronoun is very common and natural here.
Using scongelarsi can sound a bit more explicitly intransitive, but both can be understandable depending on context.

For a learner, li lascio scongelare is an excellent and very natural pattern to know.

Sul is the contraction of:

• su = on
• il = the

So:

• sul tavolo = on the table

Just like dal, this is one of the standard Italian preposition + article combinations.

Yes, here congelatore means freezer.

Italian can use:

• congelatore = freezer
• sometimes freezer as a borrowed word in informal usage

But congelatore is the standard Italian word.

It can correspond to both, depending on context.

• scongelare can mean to defrost
• or to thaw

In this sentence, because the peas are left on the table, the most natural English choice is thaw:

• I take the peas out of the freezer and leave them to thaw on the table

If you were talking about using a microwave or a machine setting, defrost might fit better.

More or less, but the most natural English translation may be a little different.

A fairly literal version is:

• I remove the peas from the freezer and leave them to thaw on the table

A more natural English version is often:

• I take the peas out of the freezer and leave them on the table to thaw

Both match the Italian meaning well. The second one sounds especially natural in English.