Wir vermeiden Datenverlust dadurch, dass wir eine Sicherungskopie speichern.

Dadurch, dass is a common German way to express by ..., through ..., or by the fact that ....

In this sentence, it introduces the method or means:

• Wir vermeiden Datenverlust ...
• ... dadurch, dass wir eine Sicherungskopie speichern.

So the second part explains how the data loss is avoided.

A very literal breakdown is:

• dadurch = through that / thereby
• dass = that

But in natural English, you usually translate the whole phrase more smoothly as by saving a backup copy.

Because dass introduces a subordinate clause, and in German subordinate clauses are normally separated from the main clause with a comma.

So here:

• main clause: Wir vermeiden Datenverlust dadurch
• subordinate clause: dass wir eine Sicherungskopie speichern

That comma is required in standard German spelling.

Because the clause starting with dass is a subordinate clause. In German, the conjugated verb in a subordinate clause usually goes to the end.

So:

• main clause: Wir vermeiden Datenverlust ...
• subordinate clause: dass wir eine Sicherungskopie speichern

Here, speichern is the finite verb of the subordinate clause, so it moves to the end.

Compare:

• Main clause: Wir speichern eine Sicherungskopie.
• Subordinate clause: ..., dass wir eine Sicherungskopie speichern.

German often uses a full subordinate clause where English might use an -ing form.

English:

• We avoid data loss by saving a backup copy.

German here:

• Wir vermeiden Datenverlust dadurch, dass wir eine Sicherungskopie speichern.

Because German is using a full dass-clause, it needs its own explicit subject: wir.

So the second wir is not optional in this structure.

Here Datenverlust is being used in a general, abstract sense, like data loss in English. German often leaves out the article with abstract or uncountable ideas when speaking generally.

So:

• Wir vermeiden Datenverlust. = We avoid data loss.

If you were talking about a specific instance, an article could appear:

• Wir vermeiden den Datenverlust dieser Dateien.

So the version without an article is normal and natural here.

It is the direct object of vermeiden, so it is in the accusative case.

The verb vermeiden is a transitive verb: it takes a direct object with no preposition.

So:

• Wir vermeiden was? → Datenverlust

That means Datenverlust is accusative.

You do not see a special ending here because:

• Datenverlust is a masculine noun
• but without an article, the accusative singular looks the same as the nominative singular

So the case is understood from the verb’s function, not from a visible change in the noun.

Because Sicherungskopie is a feminine noun.

The noun is:

• die Sicherungskopie

So in the accusative singular, the indefinite article stays:

• eine Sicherungskopie

Compare:

• masculine: einen Backup-Ordner
• feminine: eine Sicherungskopie
• neuter: ein Dokument

Here eine Sicherungskopie is the direct object of speichern.

Yes. In fact, that is often a very natural alternative.

You could say:

• Wir vermeiden Datenverlust, indem wir eine Sicherungskopie speichern.

Indem also means by doing and directly introduces the method.

The difference is roughly this:

• dadurch, dass ... = a bit more explicit, sometimes a little heavier in style
• indem ... = often more compact and elegant when describing a method

Both are correct here.

Because German forms compound nouns by joining words together into a single word.

So:

• Daten + Verlust → Datenverlust
• Sicherung + Kopie → Sicherungskopie

This is completely normal in German. English often uses separate words where German uses one compound noun.

A useful rule:

• the last part of the compound determines the gender
• der Verlust → der Datenverlust
• die Kopie → die Sicherungskopie

Yes. Vermeiden usually takes a direct accusative object.

So German says:

• Datenverlust vermeiden
• Fehler vermeiden
• Probleme vermeiden

English learners sometimes expect a preposition because English structures do not always match exactly, but in German vermeiden is straightforwardly transitive.

So this sentence is correct:

• Wir vermeiden Datenverlust ...

not something like:

• Wir vermeiden vor Datenverlust ...

Yes, it is grammatically correct and natural.

That said, many speakers might prefer the slightly shorter version:

• Wir vermeiden Datenverlust, indem wir eine Sicherungskopie speichern.

The original sentence with dadurch, dass is still perfectly good German, especially if you want to emphasize the idea of achieving something through a particular measure.