Im Garten atme ich ruhig und fühle mich besser.

German main clauses usually follow the verb-second rule. That means the finite verb must come in the second position.

So in:

Im Garten atme ich ruhig und fühle mich besser.

the first position is taken by Im Garten, so the verb atme comes next, and the subject ich follows it.

Compare:

• Ich atme im Garten ruhig.
• Im Garten atme ich ruhig.

Both are possible, but starting with Im Garten puts extra emphasis on in the garden.

Im is just the common contraction of:

• in dem → im

So:

• im Garten = in dem Garten

German uses this contraction very often, and im Garten sounds much more natural than in dem Garten in most cases.

This is about the German two-way preposition in.

With in, the case depends on whether you mean:

• location → dative
• movement toward a destination → accusative

Here, Im Garten describes a location, not movement, so German uses the dative:

• im Garten = in the garden

If the meaning were movement into the garden, you would say:

• in den Garten = into the garden

So:

• Ich bin im Garten. = I am in the garden.
• Ich gehe in den Garten. = I go into the garden.

Here ruhig functions like an adverb, describing how the speaker breathes.

German is different from English in this way: the same form is often used for both adjectives and adverbs.

So:

• ein ruhiger Mensch = a calm person
• ich atme ruhig = I breathe calmly

German does not add something like -ly. So ruhig can mean both calm and calmly, depending on context.

Because sich fühlen is a reflexive verb in German when talking about how someone feels.

So German says:

• ich fühle mich besser

literally, something like I feel myself better, though you should understand it simply as I feel better.

The reflexive pronoun changes with the subject:

• ich fühle mich
• du fühlst dich
• er/sie fühlt sich
• wir fühlen uns

This is just how the verb is normally used in German.

Besser means better, and it is very natural in German after sich fühlen.

• Ich fühle mich besser. = I feel better.

This often suggests an improvement from an earlier state.

You can also say:

• Ich fühle mich gut. = I feel good.

But besser is especially common when someone’s condition has improved.

Because both verbs share the same subject: ich.

German, like English, often does not repeat the subject when two verbs are connected by und:

• Im Garten atme ich ruhig und fühle mich besser.

This is similar to English:

• In the garden I breathe calmly and feel better.

You could repeat ich, but it would usually sound unnecessary here.

Because und is simply connecting two coordinated parts of the sentence, and in normal German, you usually do not put a comma before und.

So this is correct:

• Im Garten atme ich ruhig und fühle mich besser.

A comma would only appear in special cases, such as when full subordinate clauses or extra inserted information are involved.

Atme is the first-person singular present tense form of atmen, meaning to breathe.

The forms are:

• ich atme
• du atmest
• er/sie/es atmet
• wir atmen
• ihr atmet
• sie/Sie atmen

So atme ich in the sentence means I breathe, with the verb placed before the subject because of the verb-second rule.

Yes, that is grammatically correct.

• Ich atme im Garten ruhig und fühle mich besser.
• Im Garten atme ich ruhig und fühle mich besser.

The difference is mainly emphasis.

• Starting with Ich is more neutral.
• Starting with Im Garten highlights the place.

German often moves elements to the first position to show what is most important in the moment.

In this sentence, ruhig most naturally goes with atme:

• atme ruhig = breathe calmly

It does not normally describe fühle mich besser.

So the structure is understood like this:

• Im Garten [atme ich ruhig] und [fühle mich besser].

If you wanted to describe both actions with one adverb, German would usually make that clearer in some other way.