Die Aufgabe ist einfach, solange du ruhig bleibst.

Aufgabe is a feminine noun in German, so its nominative singular article is die. In this sentence, Die Aufgabe is the subject, so you use nominative: Die Aufgabe ist ….

• die Aufgabe (nom.) = the task
• der Aufgabe (dat.) would appear after certain prepositions or verbs, e.g. bei der Aufgabe, mit der Aufgabe.

German main clauses follow the V2 rule: the finite verb is in position 2.

• Die Aufgabe (position 1) ist (position 2) einfach (rest)

The comma is required because solange du ruhig bleibst is a subordinate clause (introduced by solange), and German uses a comma to separate subordinate clauses from the main clause.

Solange is a subordinating conjunction meaning as long as / so long as. It introduces a subordinate clause, which triggers two key things:

1. A comma before the clause.
2. The finite verb goes to the end of the subordinate clause: … solange du ruhig bleibst.

Because solange starts a subordinate clause. In subordinate clauses, German typically places the finite verb at the end:

• Main clause word order: Du bleibst ruhig.
• Subordinate clause word order: …, solange du ruhig bleibst.

Both contain the same parts; the difference is the clause type.

Functionally it’s used adverbially: it describes how you stay—calmly / calm. German often uses adjectives in an adverb-like way without changing the form:

• ruhig can mean calm (adjective) or calmly (adverbial use), but the form stays ruhig.

sein = to be (a state)
bleiben = to stay / remain (continuing a state)

So du ruhig bleibst means you remain calm (you keep that calm state), not just that you are calm at one moment.

You can, but the meaning shifts:

• solange du ruhig bleibst = the task is easy for the entire duration that you stay calm (ongoing condition).
• wenn du ruhig bleibst = the task is easy if you stay calm (more like a general conditional).

Both are grammatical; solange emphasizes duration.

Because einfach is a predicate adjective after sein:

• Die Aufgabe ist einfach. = The task is easy.

Predicate adjectives in German do not take endings. Endings appear when the adjective comes before a noun:

• eine einfache Aufgabe (adjective ending because it modifies Aufgabe directly)

Yes. You can front the subordinate clause for emphasis, but then the main clause verb still must be in position 2 (V2), so the subject comes after the verb:

• Solange du ruhig bleibst, ist die Aufgabe einfach.

Notice: subordinate clause + comma + ist + subject.

Yes. It’s the present tense conjugation of bleiben:

• ich bleibe
• du bleibst
• er/sie/es bleibt
• wir bleiben
• ihr bleibt
• sie/Sie bleiben

So du ruhig bleibst is correct.

It’s not optional in standard German. A subordinate clause introduced by solange must be separated with a comma:

• Die Aufgabe ist einfach, solange du ruhig bleibst. German comma rules are stricter than English in this area.