Fermo restando che il diritto d'autore resta valido, firmiamo.

It is a very formal, often legal or bureaucratic expression. In this sentence, fermo restando che means something like:

• it being understood that
• provided that
• without affecting the fact that
• while maintaining that

So it introduces a condition or reservation before the main action.

A natural English gloss would be something like:
Provided that the copyright remains valid, we sign or With the understanding that the copyright remains valid, we sign.

It is not the kind of phrase you usually hear in casual conversation.

In fermo restando che, the phrase is best learned as a fixed expression. Even though fermo is masculine singular, in this kind of legal formula it does not usually feel like it is directly agreeing with a visible noun in the sentence.

Historically, it comes from a participial structure with an implied idea such as ciò or questo—something like this remaining fixed/established. Because of that, learners are usually safest treating fermo restando che as a set phrase rather than analyzing it word by word every time.

So in practice:

• fermo restando che = fixed formal connector
• don’t worry too much about finding an explicit noun for fermo

Restando is the gerund of restare.

• restare = to remain, stay
• restando = remaining

So literally, fermo restando is something like remaining fixed or remaining established.

But again, in this sentence the whole expression functions idiomatically, not as a literal everyday gerund phrase.

Because they are doing two different jobs.

• restando is part of the fixed introductory expression fermo restando che
• resta is the main verb inside the subordinate clause: il diritto d'autore resta valido

So:

• fermo restando che = formal connector
• il diritto d'autore resta valido = copyright remains valid

Even though both come from restare, they are not redundant in the grammatical structure.

Il diritto d'autore is the standard Italian term for copyright.

Literally, it means the author’s right or the right of the author:

• diritto = right
• d'autore = of the author

In modern usage, though, you should understand the whole phrase as the fixed legal term copyright.

Because di is commonly shortened before a vowel.

• di autore becomes d'autore

This is called elision. Italian often drops the final vowel of certain small words before another vowel.

So:

• di + autore → d'autore

This is completely normal and standard.

Here, resta means remains, and valido is an adjective meaning valid.

• resta = remains
• valido = valid

So resta valido means remains valid.

The adjective valido agrees with il diritto d'autore, which is masculine singular:

• il diritto → masculine singular
• therefore valido → masculine singular

If the noun were feminine, the adjective would change accordingly.

Grammatically, firmiamo can mean either:

• we sign (present indicative)
• let’s sign (first-person plural exhortation)

Italian uses the same form for both.

Which meaning is intended depends on context. In a sentence like this, especially with formal or contractual wording, it could be understood as either:

• a statement: we sign
• a proposal/invitation: let’s sign

If this appears in a legal or negotiation context, the English translation might vary depending on tone.

Because Italian normally omits subject pronouns when the verb ending already makes the subject clear.

• firmiamo already tells you the subject is we
• so noi is not necessary

Italian is a pro-drop language, unlike English.

You could say noi firmiamo, but that would usually add emphasis, such as:

• we are the ones signing
• as for us, we sign

Without emphasis, just firmiamo is the normal choice.

Che introduces the clause that follows fermo restando.

So:

• fermo restando che... = it being understood that...

The clause introduced by che is:

• il diritto d'autore resta valido

In other words, che works like that in English.

The comma separates the opening formal clause from the main clause.

Structure:

• Fermo restando che il diritto d'autore resta valido = introductory subordinate/parenthetical clause
• firmiamo = main clause

So the comma helps signal: first the reservation or condition, then the main action.

In a sentence like this, the comma is very natural and helps readability, especially in formal writing.

Not really in everyday conversation. It sounds quite formal, legal, or administrative.

A native speaker might use fermo restando che in:

• contracts
• official documents
• formal negotiations
• legal discussions

In ordinary speech, people would usually choose a simpler structure, depending on the exact meaning they want, such as:

• a condizione che... = on condition that...
• purché... = provided that...
• tenendo fermo che... is less standard here, so not the best everyday replacement
• or just a clearer everyday rephrasing

So yes, it is correct, but it belongs to a high-register style.