Jeśli jutro będzie zasięg, oddzwonię do teściowej i zarezerwuję stolik w kawiarni, gdzie podają dobre gofry.

This is a very common difference between English and Polish.

In Polish, after jeśli (if), you normally use the tense that matches the real time of the situation. So if the condition is in the future, Polish uses the future tense:

• Jeśli jutro będzie zasięg... = If there is / if there will be reception tomorrow...

In English, we usually avoid will after if in this kind of sentence, but Polish does not follow that rule.

Also, będzie is third person singular because the subject is zasięg.

Here zasięg means signal, coverage, or reception, especially mobile phone reception.

So:

• jest zasięg = there is signal / there is reception
• nie ma zasięgu = there is no signal

Literally, zasięg can also mean range or reach, but in everyday speech it often refers to phone coverage.

They are future in meaning.

This happens because both verbs are perfective:

• oddzwonić = to call back, once, successfully
• zarezerwować = to reserve/book, once, successfully

In Polish, perfective verbs do not have a true present tense. Their present-looking forms refer to the future:

• oddzwonię = I will call back
• zarezerwuję = I will reserve / book

So even though the endings may look like present-tense endings, the meaning is future.

Because the verb oddzwonić is used with do + Genitive:

• oddzwonić do kogoś = to call someone back

So:

• teściowa = mother-in-law
• do teściowej = to the mother-in-law / back to the mother-in-law

The ending changes because do requires the genitive case.

Because Polish usually leaves out subject pronouns when they are obvious from the verb ending.

• oddzwonię already means I will call back
• zarezerwuję already means I will reserve

The ending -ę tells you the subject is I.

You could say Ja oddzwonię..., but that would add emphasis, something like:

• I’ll call back
• As for me, I’ll call back

Without emphasis, Polish normally drops ja.

In places like cafés and restaurants, stolik is the normal word for a table you sit at.

Technically:

• stół = table
• stolik = small table / little table

But in everyday Polish, zarezerwować stolik is the standard phrase for reserve a table. It does not necessarily mean the table is tiny. It just sounds natural in this context.

Because w meaning in / at usually takes the locative case when it refers to location.

So:

• kawiarnia = café
• w kawiarni = in the café / at the café

This is a basic case pattern:

• w domu = in the house
• w sklepie = in the shop
• w kawiarni = in the café

Gdzie means where, and here it introduces a clause describing kawiarni:

• w kawiarni, gdzie podają dobre gofry
• in a café where they serve good waffles

So gdzie works like a relative word connecting the place with more information about it.

It refers back to kawiarni.

This is a very natural Polish way to speak about an unspecified group of people.

• podają dobre gofry = they serve good waffles

The sentence does not name the subject directly. It just means the people there, the staff, or whoever runs the place.

English can do the same with they, but in translation it often sounds more natural as:

• a café that serves good waffles

So podają is plural because the understood subject is an unspecified they.

Because gofry is the direct object of podają, so it is in the accusative plural.

For this noun, the accusative plural looks the same as the nominative plural:

• gofry = waffles

The adjective has to agree with the noun:

• dobre gofry = good waffles

So the phrase is grammatically correct as the object of podają.

The commas separate subordinate clauses.

1. Jeśli jutro będzie zasięg, ...
   The if-clause comes first, so it is followed by a comma.

2. ..., w kawiarni, gdzie podają dobre gofry.
   The clause introduced by gdzie also gets a comma.

There is no comma before i because here i simply joins two coordinated verbs with the same subject:

• oddzwonię
• zarezerwuję

So:

• comma after the if-clause
• no comma before i
• comma before gdzie

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

This sentence is natural as written because it starts with the condition:

• Jeśli jutro będzie zasięg, oddzwonię...

But other orders are possible, for example if you wanted a slightly different emphasis.

Still, the original version is very normal because it presents the condition first and then the actions that depend on it.