Jeśli pomylę jeden czasownik, druga osoba i tak często rozumie całe zdanie.

Pomylę is the 1st person singular form of the perfective verb pomylić.

With perfective verbs, forms that look like present tense usually have future meaning in English. So:

• pomylę = I will mix up / I will get wrong
• in this sentence: If I get one verb wrong...

This is very common after jeśli (if). Polish often uses this structure for real, possible future situations:

• Jeśli przyjdę, zadzwonię. = If I come, I’ll call.

So Jeśli pomylę... means If I happen to make a mistake..., not If I am making a mistake...

Jeśli is used for a real or possible condition: something that may actually happen.

• Jeśli pomylę jeden czasownik... = If I get one verb wrong...
  This suggests a realistic possibility.

Gdyby is more often used for hypothetical, less likely, or contrary-to-fact situations.

Compare:

• Jeśli pomylę jeden czasownik... = If I get one verb wrong...
• Gdybym pomylił jeden czasownik... = If I were to get one verb wrong / If I got one verb wrong...

So jeśli fits a normal, practical statement better here.

Here pomylić means something like:

• to get wrong
• to mix up
• to make a mistake with

So pomylę jeden czasownik means:

• I get one verb wrong
• I use one verb incorrectly
• I mix up one verb

It does not necessarily mean that you confuse two verbs with each other in a very technical sense; it can simply mean making a mistake with one verb.

Because czasownik is the direct object of pomylić, it goes in the accusative case.

The phrase is:

• jeden czasownik = one verb

For a masculine inanimate noun like czasownik, the accusative singular looks the same as the nominative singular:

• nominative: jeden czasownik
• accusative: jeden czasownik

So even though it is accusative here, the form does not change.

Because druga osoba is the subject of the second clause:

• druga osoba ... rozumie = the other person ... understands

Subjects are in the nominative case, so we use:

• druga osoba = nominative

If it were an object, then you would see:

• drugą osobę = accusative

So here:

• druga osoba = the other person as the one doing the understanding

I tak is a very common expression meaning:

• anyway
• still
• all the same
• even so

In this sentence:

• druga osoba i tak często rozumie całe zdanie
• the other person often understands the whole sentence anyway

It adds the idea that despite the mistake, communication still often succeeds.

Examples:

• Pada, ale i tak idę. = It’s raining, but I’m going anyway.
• Nie było łatwo, ale i tak się udało. = It wasn’t easy, but it worked out anyway.

Rozumie comes from rozumieć, an imperfective verb meaning to understand.

It is used here because the sentence describes a general, repeated situation, not one completed event:

• często rozumie = often understands

Imperfective is natural for habits, regular occurrences, and general truths.

If you used a perfective verb here, it would sound more like a single completed act of understanding, which is not the point. The sentence is talking about what often happens in conversation in general.

Polish often drops subject pronouns when they are clear from the verb ending.

• pomylę already tells us the subject is I
• rozumie with druga osoba already has its subject stated

So:

• Jeśli pomylę jeden czasownik... naturally means If I get one verb wrong...

You could say Jeśli ja pomylę..., but that would add emphasis, for example:

• If I get it wrong (as opposed to someone else)

In normal speech, the pronoun is usually omitted.

Często means often, and in Polish adverbs like this are fairly flexible in position. Here it modifies rozumie:

• druga osoba i tak często rozumie całe zdanie
• the other person often understands the whole sentence anyway

This placement sounds natural and neutral.

You may also hear slightly different word orders, for example:

• druga osoba często i tak rozumie całe zdanie
• i tak druga osoba często rozumie całe zdanie

But the original order is clear and idiomatic. Polish word order is more flexible than English, but changing it can shift emphasis.

Całe zdanie means the whole sentence.

It is the direct object of rozumie, so it is in the accusative case. However, because zdanie is a neuter noun, its nominative and accusative singular forms are the same:

• nominative: całe zdanie
• accusative: całe zdanie

So the form does not visibly change.

The adjective całe agrees with zdanie in gender, number, and case:

• całe = neuter singular
• zdanie = neuter singular

In context, yes, that can be a natural English translation, especially because of i tak.

Literally, the structure is:

• Jeśli... , ... i tak...
• If... , ... anyway...

But in natural English, this often becomes:

• Even if I get one verb wrong, the other person often still understands the whole sentence.

That translation captures the contrast very well. So:

• more literal: If I get one verb wrong, the other person often understands the whole sentence anyway.
• more natural in some contexts: Even if I get one verb wrong, the other person often still understands the whole sentence.

No. In this sentence, druga osoba means the other person, not the grammar term second person.

Polish drugi / druga / drugie can mean:

• second
• other / another depending on context

Here the meaning is clearly:

• druga osoba = the other person

If you were talking about grammar, second person would usually be understood from a grammatical context, not from this everyday sentence about conversation.

Yes, it is understandable and natural enough, especially in spoken or practical learner-focused language.

It means something like:

• If I get one verb wrong, the other person often understands the whole sentence anyway.

A native speaker might also say similar versions such as:

• Jeśli pomylę jeden czasownik, druga osoba i tak często zrozumie całe zdanie.
• Jeśli źle użyję jednego czasownika, druga osoba i tak często rozumie całe zdanie.

The original sentence is perfectly usable, but Polish offers several natural ways to express the same idea depending on whether you want a more general or more one-time meaning.