Learn Hardcore German: Als das Projekt endlich gelungen war, fühlte das ganze Team eine tiefe Zufriedenheit. - When the project was finally successful, the whole team felt a deep sense of satisfaction.

Als: one specific time in the past
- Als das Projekt endlich gelungen war … = When (on that occasion) the project had finally succeeded…
Wenn: repeated events or general conditions (also used for the future)
- Wenn das Projekt gelingt, feiern wir. = When(ever) the project succeeds, we celebrate.
Wann: only for questions about time
- Wann ist das Projekt gelungen? = When did the project succeed?

So als is correct here because it refers to one particular time in the past when the project finally worked.

Why is the verb at the end in Als das Projekt endlich gelungen war?

Because Als … introduces a subordinate clause, and in German subordinate clauses the finite verb goes to the very end.

Structure of the subordinate clause:

Als (subordinating conjunction)
das Projekt (subject)
endlich (adverb)
gelungen (past participle)
war (finite verb, auxiliary) → goes last

So the pattern is: [Conjunction] + [Subject] + [Other stuff] + [Participle] + [Finite verb].

You cannot say:

✗ Als das Projekt endlich war gelungen

In subordinate clauses with compound tenses, the auxiliary (war/hatte/ist/haben) must be the last element.

Why is it gelungen war and not just gelang?

Gelungen war is the past perfect (Plusquamperfekt) of gelingen. It expresses that one past event happened before another past event:

Earlier past: das Projekt war gelungen (the project had succeeded)
Later past: das ganze Team fühlte eine tiefe Zufriedenheit (the team felt deep satisfaction)

Using the past perfect gelungen war makes the time relationship extra clear: first success, then the feeling.

You could also say:

Als das Projekt endlich gelang, fühlte das ganze Team eine tiefe Zufriedenheit.

That uses a simple past (gelang) and is also grammatically correct. The original version with gelungen war is a bit more explicit about the fact that the success was already complete when the feeling started.

Why is the auxiliary sein used (gelungen war) and not haben?

The verb gelingen (to succeed) uses sein as its auxiliary:

Das Projekt ist gelungen. = The project has succeeded.
Das Projekt war gelungen. = The project had succeeded.

Many intransitive verbs of movement or change of state use sein, for example:

Das Kind ist eingeschlafen. (The child has fallen asleep.)
Der Test ist gut gelaufen. (The test went well.)

Gelingen describes a change of state (from “not successful” to “successful”), so it takes sein, not haben.

Why is the main clause fühlte das ganze Team … and not das ganze Team fühlte …?

In a main clause, the finite verb has to be in the second position (the V2 rule). But the “first position” is not always the subject; it’s the first sentence element.

Here, the entire Als-… clause counts as the first element:

First element: Als das Projekt endlich gelungen war
Second element (must be the finite verb): fühlte
Then comes the subject: das ganze Team
Then the object: eine tiefe Zufriedenheit

So the word order must be:

Als das Projekt endlich gelungen war, fühlte das ganze Team eine tiefe Zufriedenheit.

If you remove the Als-… clause, then the subject goes first and the verb is still in second position:

Das ganze Team fühlte eine tiefe Zufriedenheit.

What cases are das ganze Team and eine tiefe Zufriedenheit, and why?

das ganze Team is nominative – it’s the subject of the main clause.
- Who felt something? → das ganze Team.
eine tiefe Zufriedenheit is accusative – it’s the direct object of fühlte.
- What did the team feel? → eine tiefe Zufriedenheit.

So the pattern is:

Subordinate clause, Subject (Nom.) + Verb + Direct object (Akk.)

German marks this with articles and adjective endings:

das ganze Team (Nom. neuter singular)
eine tiefe Zufriedenheit (Akk. feminine singular; same form as Nom. for feminine)

Why is it das ganze Team and not das ganz Team?

Because ganz is an adjective here and adjectives before a noun need an ending that agrees with gender, number, and case.

Team is neuter.
It’s the subject, so nominative singular.
With the definite article das, the correct ending for an attributive adjective is -e.

So we get:

das ganze Team = the whole team

Without the ending (das ganz Team) would be ungrammatical.

Why is it eine tiefe Zufriedenheit and not eine tief Zufriedenheit?

Again, tief is an adjective placed in front of a noun, so it must take an adjective ending.

Zufriedenheit is feminine.
The phrase is a direct object, so accusative singular.
With eine (indefinite article, feminine, singular, nominative/accusative), the adjective ending is -e.

So:

eine tiefe Zufriedenheit = a deep satisfaction

Eine tief Zufriedenheit is incorrect because the adjective is missing its required ending.

Why is the comma necessary before fühlte?

In German, you must place a comma between a subordinate clause and a main clause.

Als das Projekt endlich gelungen war, → subordinate clause
fühlte das ganze Team eine tiefe Zufriedenheit. → main clause

The comma marks the boundary between the two. This rule is obligatory in standard written German, unlike in English where comma use is more flexible.

Why is the adverb endlich placed after das Projekt and not somewhere else?

Adverbs like endlich usually go after the subject and before the verb complex or before the element they modify most closely.

In the subordinate clause:

Subject: das Projekt
Adverb: endlich
Verb parts: gelungen war

Als das Projekt endlich gelungen war is natural and typical word order.

You could also say:

Als das Projekt gelungen war, (without endlich)
Als endlich das Projekt gelungen war, (possible, but now endlich is strongly emphasised)

The original position (das Projekt endlich gelungen war) sounds neutral and idiomatic.

Why use Zufriedenheit (a noun) instead of zufrieden (an adjective), as in war sehr zufrieden?

Both structures are possible, but they differ slightly in style and nuance:

eine tiefe Zufriedenheit fühlen
- Verb of feeling + abstract noun
- Sounds a bit more formal or literary.
- Emphasizes the state as something almost “tangible”.
sehr zufrieden sein
- sein
  - adjective
- More everyday, straightforward description of how someone is.

Compare:

Das ganze Team war sehr zufrieden. = The whole team was very satisfied.
Das ganze Team fühlte eine tiefe Zufriedenheit. = The whole team felt a deep sense of satisfaction.

The original sentence chooses the more expressive, slightly more elevated noun phrase.

Why is the verb fühlte in the simple past and not hat gefühlt?

In written narrative German, especially in stories, reports, and books, the Präteritum (simple past) is preferred for most verbs:

fühlte = felt (simple past)
hat gefühlt = has felt (present perfect)

Spoken German often prefers the Perfekt:

Spoken: Das ganze Team hat eine tiefe Zufriedenheit gefühlt.
Written narrative: Das ganze Team fühlte eine tiefe Zufriedenheit.

So using fühlte here matches normal written narrative style.

Is fühlen eine tiefe Zufriedenheit the normal way to talk about emotions in German?

It’s one common pattern, especially in more formal or literary language:

Freude / Angst / Wut / Zufriedenheit fühlen
- Er fühlte große Freude.
- Sie fühlte Angst.

Colloquially, Germans also use:

sein + Adjective:
- Sie waren zufrieden.
- Er war glücklich.
Empfinden (to feel, experience):
- Er empfand eine tiefe Zufriedenheit. (even more formal)

So fühlte eine tiefe Zufriedenheit is correct and idiomatic, just slightly more expressive/formal than everyday war sehr zufrieden.