Learn Hardcore German: Mein Bruder bleibt optimistisch, obwohl ich manchmal frustriert bin. - My brother stays optimistic, although I am sometimes frustrated.

ist optimistisch = is optimistic (a simple description of his current state or character).
bleibt optimistisch = stays / remains optimistic (highlights that he continues to be optimistic despite something).

In this sentence, bleibt stresses the contrast: even though I am sometimes frustrated, my brother remains optimistic. The verb bleiben often emphasizes continuity in the face of difficulties or change.

Why is there a comma before obwohl?

In German, obwohl introduces a subordinate clause (a dependent clause). Subordinate clauses are always separated from the main clause by a comma.

Main clause: Mein Bruder bleibt optimistisch
Subordinate clause: obwohl ich manchmal frustriert bin

So the comma marks the boundary between the independent statement and the obwohl clause that gives contrasting information.

Why is the verb bin at the end of the clause obwohl ich manchmal frustriert bin?

In German, subordinate clauses introduced by conjunctions like obwohl, weil, dass, etc., follow the pattern:

Subject – (other elements) – verb at the end

So in this clause:

Subject: ich
Adverb: manchmal
Predicate adjective: frustriert
Finite verb: bin (goes to the end because of obwohl)

That’s why you get: obwohl ich manchmal frustriert bin, not obwohl ich bin manchmal frustriert.

Could the sentence start with obwohl? How would the word order change?

Yes, you can start with the obwohl-clause. Then the main clause must obey the “verb in second position” rule, which causes inversion:

Obwohl ich manchmal frustriert bin, bleibt mein Bruder optimistisch.

Notice that after the subordinate clause, the next first element is the entire obwohl-clause, so the conjugated verb bleibt must come immediately after it. You cannot say:

❌ Obwohl ich manchmal frustriert bin, mein Bruder bleibt optimistisch.

Why is it Mein Bruder and not something like Meinem Bruder?

Mein Bruder is in the nominative case, because it is the subject of the main clause — the person who bleibt optimistisch.

Wer bleibt optimistisch? – Mein Bruder. (Who remains optimistic? My brother.)

If the brother were the indirect object, you might see meinem Bruder (dative), but here he performs the action, so nominative is required.

In obwohl ich manchmal frustriert bin, why is it ich and not mich?

Ich is the nominative form of the pronoun, and it’s the subject of the subordinate clause:

Wer ist manchmal frustriert? – Ich.

Mich would be the accusative form, used as a direct object (for example: Er sieht mich – He sees me). Since here “I” am the one who “am frustrated,” the nominative ich is correct.

Why are optimistisch and frustriert not capitalized or used with any article?

They are adjectives used as predicate adjectives, linked to the subject by a form of sein or bleiben:

Mein Bruder bleibt optimistisch.
Ich bin frustriert.

In German:

Predicate adjectives are not capitalized.
They are not preceded by an article (no ein or der), unlike nouns.

If you turned them into nouns, they would be capitalized, e.g. der Optimist, die Frustration.

Why is it manchmal frustriert and not frustriert manchmal, and could you change the order?

The standard and most natural order for adverbs of time is before the adjective phrase:

ich bin manchmal frustriert

Within the subordinate clause: ich manchmal frustriert bin.

You could say ich bin frustriert, manchmal, but that usually has a different rhythm or emphasis, often sounding like an afterthought. Inside the obwohl-clause, ich manchmal frustriert bin is the normal neutral order.

So:

Neutral: obwohl ich manchmal frustriert bin
Marked / emphatic: obwohl ich frustriert bin, manchmal (unusual and more spoken/emphatic).

What is the difference between obwohl and trotzdem in this kind of sentence?

Both express a contrast, but they work differently:

obwohl = although / even though
It introduces a subordinate clause:
- Mein Bruder bleibt optimistisch, obwohl ich manchmal frustriert bin.
trotzdem = nevertheless / in spite of that
It is an adverb that usually starts the main clause after a full clause:
- Ich bin manchmal frustriert, trotzdem bleibt mein Bruder optimistisch.

You can often paraphrase an obwohl sentence with a trotzdem construction, but the grammar changes (conjunction vs. adverb).

How are bleibt and bin formed? What are their infinitives and persons?

bleibt comes from the infinitive bleiben (to stay / remain).
- ich bleibe
- du bleibst
- er/sie/es bleibt ← used here (Mein Bruder bleibt)
- wir bleiben
- ihr bleibt
- sie/Sie bleiben
bin comes from the infinitive sein (to be).
- ich bin ← used here (ich … bin)
- du bist
- er/sie/es ist
- wir sind
- ihr seid
- sie/Sie sind

So the sentence uses 3rd person singular for bleiben and 1st person singular for sein.

Could you change the tense to say “although I am sometimes frustrated (in the past)”?

To put the subordinate clause in the past while keeping the main clause in the present, you could use the Perfekt or Präteritum for sein:

Mein Bruder bleibt optimistisch, obwohl ich manchmal frustriert war.
(Präteritum – although I was sometimes frustrated.)

Mein Bruder bleibt optimistisch, obwohl ich manchmal frustriert gewesen bin.
(Perfekt – grammatically correct but sounds more formal/less common in everyday speech here.)

In spoken German, war is usually preferred for such a simple “was” in the past.