Learn Hardcore German: Wegen ihrer Ehrlichkeit fällt es uns leicht, auch über schwierige Themen zu reden und als Gruppe zusammenzuhalten. - Because of her honesty it is easy for us to talk about difficult topics as well and to stick together as a group.

es – dummy / anticipatory subject
uns – dative pronoun = for us
leicht – predicate adjective = easy
auch über schwierige Themen zu reden und als Gruppe zusammenzuhalten – the real content (= what is easy)

Literally:

Es fällt uns leicht, …
= It falls easy to us (to) …
→ idiomatic English: It is easy for us to … / We find it easy to …

This is a very common German structure:

Es fällt mir schwer, früh aufzustehen.
It’s hard for me to get up early.

Why is it uns and not wir in fällt es uns leicht?

Because uns is in the dative case, and the verb pattern requires dative:

Pattern: jemandem fällt etwas leicht
- jemandem = dative (to someone)
- etwas = subject (the thing that is easy)

In your sentence:

es – grammatical subject (dummy “it”)
uns – dative object (to us / for us)

Compare:

Es fällt mir leicht. – It is easy for me.
Es fällt dir leicht. – It is easy for you.
Es fällt uns leicht. – It is easy for us.

Using wir would be nominative (we) and doesn’t fit this verb pattern.

What exactly is going on with wegen ihrer Ehrlichkeit? Why ihrer, and which case is this?

Wegen is a preposition that traditionally takes the genitive:

wegen
- genitive → wegen ihrer Ehrlichkeit

Here:

Ehrlichkeit – feminine noun (= honesty)
ihrer – possessive pronoun referring to her / their / your (formal)
ihrer Ehrlichkeit – genitive (or dative; see below) singular feminine

So wegen ihrer Ehrlichkeit = because of her/their/your honesty.

Formally:

Genitive feminine singular of ihre is ihrer.
Dative feminine singular is also ihrer.
So purely by form, ihrer Ehrlichkeit could be genitive or dative. With wegen, standard written German intends it as genitive.

Because the person is not specified here, ihrer could mean:

because of *her honesty*
because of *their honesty*
because of *your honesty (formal *Sie)

Only context can disambiguate that.

Can wegen also use the dative instead of the genitive? Would that change the sentence?

Yes. In spoken and informal written German, wegen very often takes the dative:

wegen der Ehrlichkeit (genitive or dative, forms coincide here)
wegen meiner Freunde (standard genitive)
→ colloquial: wegen meinen Freunden (dative)

In your sentence, wegen ihrer Ehrlichkeit is perfectly fine as standard written German with the genitive, but colloquial speakers often wouldn’t even notice or care whether it’s genitive or dative because the form ihrer works for both.

Meaning does not change; it’s a stylistic/formality issue:

Standard: wegen ihrer Ehrlichkeit (intended as genitive)
Colloquial: people might think of it as dative, but they say the same string of words.

Why is the verb fällt in second position after Wegen ihrer Ehrlichkeit? Could I also say Es fällt uns wegen ihrer Ehrlichkeit leicht?

German main clauses follow the V2 rule: the finite verb (here fällt) must be in second position (second slot), no matter how long the first element is.

Your sentence:

Wegen ihrer Ehrlichkeit – first element (fronted adverbial phrase)
fällt – conjugated verb in second position
es uns leicht, … – the rest of the clause

This word order emphasizes the cause (wegen ihrer Ehrlichkeit) at the beginning.

You can say:

Es fällt uns wegen ihrer Ehrlichkeit leicht, …

Here:

Es – first element
fällt – verb (still second)
uns wegen ihrer Ehrlichkeit leicht, … – rest

Both are correct; the difference is mainly focus/emphasis.

Why is there a comma before auch über schwierige Themen zu reden …?

Because auch über schwierige Themen zu reden und als Gruppe zusammenzuhalten is an infinitive clause with zu, and German normally sets a comma before such a clause when it is expanded (i.e. not just a bare infinitive):

Es fällt uns leicht, auch über schwierige Themen zu reden.
Es ist wichtig, ehrlich zu sein.
Wir haben beschlossen, früher zu gehen.

The comma separates the main clause:

Wegen ihrer Ehrlichkeit fällt es uns leicht,

from the infinitive clause:

auch über schwierige Themen zu reden und als Gruppe zusammenzuhalten.

How does zu work with reden and with zusammenzuhalten? Why is zu inside the second verb?

German has two patterns here:

Simple verb → zu just goes in front:
- reden → zu reden
- lernen → zu lernen
Separable-prefix verb (like zusammenhalten):
- Base form: zusammenhalten
- In infinitive with zu, the zu goes between prefix and stem:
  - zusammenhalten → zusammenzuhalten
    (zusammen + zu + halten)

So in your sentence:

zu reden – simple verb
zusammenzuhalten – separable-prefix verb with zu in the middle

This is the standard rule for all separable verbs:

aufstehen → aufzustehen
ankommen → anzukommen
mitmachen → mitzumachen

Why is zusammenzuhalten written as one word? What does zusammenhalten mean exactly?

Zusammenhalten is a separable-prefix verb:

Prefix: zusammen- (together)
Verb: halten (hold)

Meaning:

zusammenhalten ≈ to stick together, to stay united, to hold together as a group

In dictionaries and in the infinitive, these verbs are written as one word:

zusammenhalten, aufstehen, mitmachen, zurückkommen, etc.

But in a main clause, when conjugated, the prefix separates and moves to the end:

Wir halten als Gruppe zusammen. – We stick together as a group.
Sie steht früh auf. – She gets up early.

In your sentence, you have an infinitive with zu, so it stays as zusammenzuhalten (one word, with zu inside).

Why is it als Gruppe and not wie eine Gruppe or in der Gruppe?

Als in this context means “as (in the role of / in the function of)”:

als Gruppe – as a group (in our role/identity as a group)

Comparisons:

als – with nouns, often means as (function/role):
- als Lehrer arbeiten – to work as a teacher
- als Team auftreten – to appear as a team
- als Gruppe zusammenhalten – to stick together as a group
wie – comparison: like / as … as
- wie eine Gruppe – like a group (similar to a group, but not necessarily actually one)
in der Gruppe – location/membership:
- in der Gruppe – in the group / within the group

So:

als Gruppe zusammenhalten emphasizes acting in the role of a group, united as one entity.
in der Gruppe zusammenhalten would slightly shift the focus to “within the group,” but als Gruppe is the more idiomatic phrasing for “to stick together as a group.”

Why is it über schwierige Themen reden? Why über and which case does it take?

With the verb reden, both über and von are possible, but they differ slightly:

über + Akkusativ:
- more like about, often slightly more explicit/topic-focused
- über Politik reden – talk about politics
von + Dativ:
- more like of, sometimes more general or personal
- von dir reden – talk about you

In your sentence:

(über) schwierige Themen – Akkusativ plural after über
- Nominative: schwierige Themen
- Accusative plural is the same: schwierige Themen

So über here governs the accusative:

über schwierige Themen (Akk.) reden – to talk about difficult topics

Why is the adjective schwierige ending with -e in schwierige Themen?

Themen is plural, neuter plural (from das Thema). Adjective endings in plural are same for all genders; what matters is case and article type.

Here:

Article: keine article before schwierige Themen (no die, no meine)
Case: Akkusativ plural (object of über)
Pattern: no article + accusative plural → adjective ending -e

So:

schwierige Themen – difficult topics (accusative plural, no article)

Compare:

die schwierigen Themen – definite article (Akk. Pl.)
meine schwierigen Themen – possessive article (Akk. Pl.)
schwierige Themen – no article (Akk. Pl.)

What does auch do in es fällt uns leicht, auch über schwierige Themen zu reden … and where can it go?

Auch means also / even / too and here it emphasizes that not only easy topics, but even difficult topics are easy to talk about.

Position in your sentence:

… fällt es uns leicht, auch über schwierige Themen zu reden …

Placing auch directly before über schwierige Themen makes it clear that what is being added/emphasized is “difficult topics as well”.

You could move it slightly:

… fällt es uns auch leicht, über schwierige Themen zu reden …
Here auch is attached more to fällt es uns leicht, meaning It is also easy for us (in addition to something else) to talk about difficult topics.

So:

auch über schwierige Themen → focus on the topics: even difficult topics
es fällt uns auch leicht → focus on the fact: this is also easy for us

In the given sentence, the writer clearly wants to stress even difficult topics.