Learn Hardcore German: Viel Erfolg morgen! – Gleichfalls! - Good luck tomorrow!

Yes. It’s a standard elliptical well‑wish. The full sentence would be Ich wünsche dir/Ihnen viel Erfolg (morgen). In everyday German, wishes like this routinely drop the subject and verb.

Why is morgen lowercase here? What would Morgen mean?

Lowercase morgen is the adverb “tomorrow.” Capitalized Morgen is the noun “morning.” Note: at the start of a sentence you’ll see Morgen capitalized anyway, so context tells you whether it means “tomorrow” or “morning.”

Could I say Viel Erfolg am Morgen! if I mean “tomorrow”?

No. am Morgen means “in the morning,” not “tomorrow.” To express “tomorrow,” use lowercase morgen: Viel Erfolg morgen!

Is Viel Erfolg morgen! idiomatic, or should I add a preposition like für or bei?

It’s idiomatic as is. Alternatives:

Viel Erfolg für morgen! (a bit more explicit about the time)
Viel Erfolg bei der Prüfung morgen! (when naming the activity: bei + activity)

Where can I put morgen? Are other word orders correct?

In this fixed formula, Viel Erfolg morgen! is the most natural. You may also hear Morgen viel Erfolg! In a full sentence, typical orders include Ich wünsche dir morgen viel Erfolg or Für morgen wünsche ich dir viel Erfolg.

What’s the difference between Viel Erfolg! and Viel Glück!?

Viel Erfolg! = “Much success!” Emphasizes outcome earned through skill/preparation (exams, interviews, presentations).
Viel Glück! = “Good luck!” Emphasizes luck/chance. For many situations (exams, surgery), both are used; Viel Erfolg! feels a touch more about performance.

Is Gleichfalls! polite, and can I use it both formally and informally?

Yes. Gleichfalls! is neutral, brief, and fine in both formal and informal contexts. Many people say Danke, gleichfalls! as a courteous reply.

What’s the difference between gleichfalls and ebenfalls?

Both mean “likewise.” Ebenfalls can feel slightly more formal; gleichfalls slightly more conversational, but they’re interchangeable in most replies: Schönes Wochenende! — Ebenfalls!/Gleichfalls!

Can I reply with Dir auch! or Ihnen auch! instead of Gleichfalls!?

Yes. Use the pronoun that matches your relationship:

Informal singular: Danke, dir auch!
Informal plural: Danke, euch auch!
Formal: Danke, Ihnen auch! Using Gleichfalls! neatly avoids choosing a pronoun.

Should I always reply with Gleichfalls!, or only if the wish applies to me too?

Only if it applies to you as well. If it doesn’t, just say Danke! For example, after Gute Besserung! you normally don’t say Gleichfalls! unless the other person is also ill.

How do you pronounce the words?

viel: [fiːl] — the initial letter is pronounced like English “f,” long ee sound; “feel.”
Erfolg: [ɛʁˈfɔlk] — stress on the second syllable; final “g” is devoiced like “k.”
morgen: [ˈmɔʁɡn̩] — stress on the first syllable; clear “g.”
gleichfalls: [ˈɡlaɪ̯çfals] — “ei” like English “eye,” “ch” is a soft, hissy sound (as in ich), final “s” is unvoiced.

Why is Erfolg capitalized but viel and gleichfalls are not?

German capitalizes nouns, and Erfolg is a noun. viel is a determiner/adverb, and gleichfalls is an adverb, so both are lowercase (unless they start a sentence).

Do I need a comma: Viel Erfolg, morgen!?

No. That comma would suggest morgen is a form of address (as if speaking to someone named “Morgen”). The correct wish is written without a comma: Viel Erfolg morgen!

Can I say Viele Erfolge morgen!?

Not for this meaning. Erfolge (plural) means “achievements” and sounds odd here. The idiomatic wish is Viel Erfolg! Example where the plural is fine: Er hat viele Erfolge in seiner Karriere erzielt.

Is Gleichfalls one word? Any hyphenated variants?

It’s always one word: gleichfalls (lowercase unless at sentence start). Don’t split or hyphenate it.

How can I make the wish more specific?

Add the activity with bei (or beim), and keep morgen if needed:

Viel Erfolg bei der Prüfung morgen!
Viel Erfolg beim Vorstellungsgespräch morgen!
Viel Erfolg morgen beim Spiel!

Is the exclamation mark required?

Not required, but standard for wishes in German. A period is possible but feels flatter; Viel Erfolg morgen! reads most naturally with the exclamation mark.