Ufam naszej lekarce, bo zawsze wszystko spokojnie wyjaśnia.

Because ufać means to trust and it requires the dative case in Polish.

• dictionary form: lekarka = female doctor
• dative singular: lekarce = to/for the female doctor

So:

• Ufam lekarce = I trust the doctor

This is one of those verb patterns you simply need to learn:

• ufać komuś = to trust someone
• pomagać komuś = to help someone
• dziękować komuś = to thank someone

All of them take the dative.

For the same reason: naszej has to match lekarce.

Since lekarce is:

• feminine
• singular
• dative

the possessive word must also be:

• feminine
• singular
• dative

So:

• nasza lekarka = our doctor (subject/basic form)
• ufam naszej lekarce = I trust our doctor

The adjective/possessive changes to agree with the noun.

Yes. Lekarka is specifically a female doctor.

Compare:

• lekarz = doctor (masculine form; can also sometimes be used generically)
• lekarka = female doctor

In your sentence, the speaker is clearly referring to a woman.

Because bo introduces another clause, and in standard Polish it is normally separated by a comma.

So:

• Ufam naszej lekarce, bo zawsze wszystko spokojnie wyjaśnia.

This is very normal Polish punctuation, just like English often uses a comma before because in some sentence structures.

Both can mean because, but they differ in style.

• bo = common, everyday, conversational
• ponieważ = a bit more formal or written

So this sentence sounds natural and everyday with bo:

• Ufam naszej lekarce, bo...

You could also say:

• Ufam naszej lekarce, ponieważ...

That is also correct, just slightly more formal.

Because wszystko means everything as a pronoun.

• wszystko = everything
• wszystkie = all / all of them, usually agreeing with plural non-masculine-personal nouns

Here, the meaning is:

• she explains everything

So wszystko is exactly the right form.

Examples:

• Wszystko rozumiem. = I understand everything.
• Wszystkie książki są nowe. = All the books are new.

Spokojnie is an adverb meaning something like:

• calmly
• in a calm way
• sometimes patiently or without rushing, depending on context

It comes from the adjective:

• spokojny = calm

So:

• spokojnie wyjaśnia = explains calmly

It describes how she explains things.

Because wyjaśnia is the imperfective verb form, and it fits the idea of something habitual or repeated.

The sentence says:

• she always explains everything calmly

That is a repeated action, so Polish normally uses the imperfective:

• wyjaśniać → wyjaśnia
• meaning: explains / is in the habit of explaining

By contrast:

• wyjaśni is perfective future
• it means will explain

So:

• zawsze wszystko wyjaśnia = she always explains everything
• wszystko wyjaśni = she will explain everything

Because in Polish, just like in English, the present tense is used for regular or habitual actions.

So:

• zawsze wszystko spokojnie wyjaśnia literally uses present tense
• but the meaning is she always explains everything calmly

This is a normal way to describe someone's typical behavior.

Not completely. Polish word order is fairly flexible, but the version in your sentence sounds natural and neutral.

Current order:

• bo zawsze wszystko spokojnie wyjaśnia

This roughly gives:

• because she always explains everything calmly

You may also hear other orders, for example:

• bo wszystko zawsze spokojnie wyjaśnia
• bo spokojnie wszystko zawsze wyjaśnia

But the original version is the most straightforward and natural for a learner to copy.

Yes. Polish often omits subject pronouns when the verb form already makes the subject clear.

In:

• wyjaśnia

the verb already tells you it means:

• he/she/it explains

From context, because we are talking about naszej lekarce, we understand it as she explains.

If you added ona, it would usually sound more emphatic:

• bo ona zawsze wszystko spokojnie wyjaśnia

That is possible, but not necessary.

Usually, no. For trust someone, the natural verb is ufać.

• ufać komuś = to trust someone

The verb wierzyć often means:

• to believe
• to believe someone / what someone says
• to have faith

So:

• Ufam naszej lekarce = I trust our doctor
• Wierzę naszej lekarce = I believe our doctor / I believe what our doctor says

They are related ideas, but not identical. In your sentence, ufać is the best choice.

It is in the accusative, because it is the direct object of wyjaśnia.

She explains what?

• wszystko = everything

With everything, the nominative and accusative forms are the same:

• wszystko

So even though the form does not change visibly here, its role in the sentence is that of a direct object.

Yes.

• Ufam lekarce, bo zawsze wszystko spokojnie wyjaśnia.

This means:

• I trust the doctor, because she always explains everything calmly.

Adding naszej means our doctor, so it gives a more specific, personal context. It suggests the speaker and listener share the same doctor, or the speaker is speaking from the perspective of a group or family.