Η βεβαιότητα ότι όλα είναι καλά με κάνει να νιώθω πιο ήρεμος.

It breaks down like this:

• Η βεβαιότητα ότι όλα είναι καλά = the certainty that everything is fine
• με κάνει = makes me
• να νιώθω πιο ήρεμος = feel calmer / feel more calm

So the pattern is:

[subject] + με κάνει + να + verb

A very useful chunk to learn is:

• κάτι με κάνει να... = something makes me...

For example:

• Αυτό με κάνει να χαμογελώ. = That makes me smile.

βεβαιότητα means certainty or assurance.

The article η is there because the noun phrase is the subject of the sentence:

• Η βεβαιότητα ότι όλα είναι καλά = The certainty that everything is fine

Greek often uses the definite article more naturally than English, including with abstract nouns. So even where English might sometimes say certainty, Greek often prefers η βεβαιότητα.

Also, βεβαιότητα is a feminine noun, so it takes η.

Here ότι means that and introduces a content clause:

• ότι όλα είναι καλά = that everything is fine

So the sentence is talking about the certainty that something is true.

A useful thing to remember:

• ότι = that
• ό,τι = whatever / anything that

Those are different words.

So in this sentence, it is definitely ότι = that.

Because όλα literally means all things.

So Greek often expresses everything with the neuter plural όλα.

Then:

• όλα = everything / all things
• καλά = fine / good / okay

So όλα είναι καλά literally looks like all things are fine, even though in English we usually say everything is fine.

This is very natural Greek.

In this sentence, καλά is best understood as an adjective used predicatively:

• όλα είναι καλά = everything is fine / okay

It has the same form as the adverb καλά meaning well, which can be confusing.

Compare:

• Είμαι καλά. = I am well / I’m okay.
• Όλα είναι καλά. = Everything is fine.

So although the form is the same, here it is part of the expression meaning things are okay/fine.

με means me.

It is the weak object pronoun, so:

• με κάνει = it makes me

And κάνει is from κάνω = to do / to make.

So:

• Η βεβαιότητα ... με κάνει ... = The certainty ... makes me ...

This is a very common structure in Greek:

• με κάνει να γελάω = it makes me laugh
• με κάνει να σκέφτομαι = it makes me think
• με κάνει να νιώθω καλύτερα = it makes me feel better

Because Modern Greek does not use the infinitive the way English does.

Where English says:

• makes me feel

Greek normally says:

• με κάνει να νιώθω

The word να introduces a subordinate verb form, often called the subjunctive construction.

So:

• να νιώθω = to feel / that I feel in this kind of structure

You should get used to patterns like:

• θέλω να πάω = I want to go
• μπορώ να έρθω = I can come
• με κάνει να νιώθω = it makes me feel

Because the Greek present here expresses an ongoing or general state:

• με κάνει να νιώθω πιο ήρεμος = it makes me feel calmer

It is not about one single completed moment. It describes the effect the certainty has on the speaker.

If you changed the tense, the meaning would change too. But in this sentence, the present is the natural choice.

πιο means more, so:

• πιο ήρεμος = more calm / calmer

This is the most common way to form the comparative in everyday Greek:

• πιο καλός = better
• πιο μεγάλος = bigger
• πιο ήρεμος = calmer

Greek does also have some one-word comparative forms, but πιο + adjective is extremely common and natural.

Because the adjective agrees with the person who is feeling calm — the speaker, the implied I.

So if the speaker is male:

• νιώθω πιο ήρεμος

If the speaker is female:

• νιώθω πιο ήρεμη

That is because adjectives in Greek agree in gender and number.

So this sentence, as written, suggests a male speaker.

A female version would be:

• Η βεβαιότητα ότι όλα είναι καλά με κάνει να νιώθω πιο ήρεμη.

Yes.

You could say:

• ...με κάνει να αισθάνομαι πιο ήρεμος.

That also means ...makes me feel calmer.

Very roughly:

• νιώθω is extremely common and everyday
• αισθάνομαι is also common, but can sound a little more formal or reflective depending on context

In most situations, both work.

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

The original sentence is natural and neutral:

• Η βεβαιότητα ότι όλα είναι καλά με κάνει να νιώθω πιο ήρεμος.

You could also move things around for emphasis, for example:

• Με κάνει να νιώθω πιο ήρεμος η βεβαιότητα ότι όλα είναι καλά.

That is still grammatical, but the original version is the most straightforward for a learner.

Yes. Even though the literal structure is useful to learn, a natural English-style understanding is:

• Knowing that everything is fine makes me feel calmer.
• The certainty that everything is okay makes me feel more relaxed.

So in Greek, the sentence uses the noun βεβαιότητα (certainty / assurance) where English might sometimes prefer a clause like knowing that.... Both ways are perfectly normal ways to express the idea.