Jeg klarer å holde meg rolig, selv om jeg er nervøs.

Both can translate to can, but they lean different ways:

• jeg kan = ability/permission in general: I can (I’m able to / I know how to).
• jeg klarer å = succeeding in doing it (often despite difficulty): I manage to / I can manage to.

In this sentence, klarer highlights that staying calm is an achievement even though the speaker is nervous.

Because the speaker is “keeping” themselves calm. Norwegian expresses this with a reflexive pronoun:

• holde meg rolig = keep myself calm
• holde deg rolig = keep yourself (you) calm
• holde seg rolig = keep oneself / themselves calm

Without the pronoun, it sounds incomplete or like you’re keeping something else calm.

In holde meg rolig, rolig describes the state of meg (me). It functions like a “resulting state” complement:

• holde meg rolig ≈ keep me (in a) calm state

Norwegian often uses an adjective here where English might choose an adverb:

• English: stay calm / keep calm
• Norwegian: holde seg rolig / holde seg calm (but rolig is the normal word)

• holde meg rolig = keep myself calm (actively maintaining calmness)
• være rolig = be calm (more like a state, not necessarily effortful)
• forbli rolig = remain calm (also common)

holde meg rolig suggests self-control during something challenging.

selv om means even though / although and introduces a contrast:

• X, selv om Y = X happens despite Y.

It’s different from:

• fordi (because) = gives a reason
• men (but) = coordinates two main clauses, not a subordinate “although” clause

So: I stay calm, even though I’m nervous (contrast), not because I’m nervous.

Norwegian normally uses a comma before subordinate clauses introduced by conjunctions like selv om, fordi, når, hvis, etc., especially when the subordinate clause comes after the main clause:

• Jeg klarer å holde meg rolig, selv om jeg er nervøs.

(If the subordinate clause comes first, you also use a comma after it.)

Yes: selv om introduces a subordinate clause, and in subordinate clauses Norwegian keeps the normal subject–verb order:

• ... selv om jeg er nervøs (subject jeg
  • verb er)

The big word-order change in Norwegian subordinate clauses is usually where adverbs like ikke go (they come before the verb), but this sentence doesn’t include such an adverb.

Yes, that’s fully correct and very natural.
When a subordinate clause comes first, the main clause must have inversion (verb in second position), so you get:

• Selv om jeg er nervøs, klarer jeg å holde meg rolig.
  (not ... jeg klarer ...)

Norwegian commonly uses være (to be) with adjectives for feelings/states:

• jeg er nervøs = I’m nervous
• jeg er trøtt = I’m tired
• jeg er glad = I’m happy

You can say jeg føler meg nervøs (I feel nervous), but jeg er nervøs is often the simplest, most idiomatic.

Both exist but differ:

• nervøs = nervous (often anxious/uneasy)
• spent = excited/tense/in anticipation; can be positive or neutral

So the sentence would change nuance if you swap it:

• ... selv om jeg er spent = even though I’m excited/tense (not necessarily anxious)

A common neutral pattern is:

• Stress on content words: klarer, holde, rolig, nervøs
• selv om is usually lighter, linking the contrast

Approximate rhythm (not a perfect phonetic guide):
Jeg KLArer å HOl-de meg RO-lig, selv om jeg er ner-VØS.