Dejamos de revisar el refresco de la masa madre.

It means to stop doing something.

So:

• dejamos de revisar = we stop checking or we stopped checking

This is a very common Spanish structure:

• dejar de fumar = to stop smoking
• dejar de hablar = to stop talking
• dejar de revisar = to stop checking/reviewing

Because dejar de + infinitive is a fixed expression.

That de is not optional here. It changes the meaning of dejar:

• dejar on its own can mean to leave, to let, or to allow
• dejar de + infinitive means to stop doing

Compare:

• Dejamos el libro = we left the book
• Dejamos de leer el libro = we stopped reading the book

So in your sentence, de is required.

It can mean either one, depending on context.

For nosotros, the form dejamos is the same in:

• present indicative: we stop / we leave
• preterite: we stopped / we left

So without more context, Dejamos de revisar... could mean:

• We stop checking...
• We stopped checking...

Usually the wider context tells you which one is intended.

Because Spanish often leaves out subject pronouns when the verb already makes the subject clear.

• Dejamos already tells you the subject is we
• So nosotros is unnecessary unless the speaker wants emphasis or contrast

For example:

• Dejamos de revisar... = normal, neutral
• Nosotros dejamos de revisar... = more emphatic, like we stopped checking

This is very common in Spanish.

Usually, no. Revisar is often a false friend for English speakers.

In most contexts, revisar means:

• to check
• to inspect
• to look over
• to review/examine

In this sentence, it most likely means to check or inspect.

So revisar el refresco de la masa madre is something like:

• checking the sourdough starter’s refreshment/feeding
• inspecting how the refresh/feed is going

It usually does not mean to revise in the English sense of editing or rewriting.

Here, refresco is a bread-making term, not a drink.

In everyday Spanish, refresco often means:

• soft drink
• soda

But in the context of masa madre, refresco means the refreshment or feeding of the sourdough starter.

So it refers to the process or result of refreshing the starter by adding flour and water.

That is why context matters a lot with this word.

Masa madre is the usual Spanish term for sourdough starter.

Literally, it means something like mother dough, but in normal usage it simply means the starter used to make sourdough bread.

It is a fixed expression, and it is feminine:

• la masa madre

Examples:

• La masa madre está lista = the sourdough starter is ready
• Alimentamos la masa madre = we feed the sourdough starter

Because the sentence is referring to a specific refreshment/feeding, not just any one.

• el refresco = the refreshment/feeding
• un refresco = a refreshment/feeding

Using el suggests that the speaker and listener already know which refreshment or feeding is being talked about.

Also, Spanish often uses the definite article more than English does, especially when something is understood from context.

Spanish often prefers noun + de + noun where English might use a possessive.

So:

• el refresco de la masa madre = the sourdough starter’s refreshment/feeding

This is very natural in Spanish.

Using su could be more ambiguous, because su can mean:

• his
• her
• its
• your
• their

So de la masa madre is clearer.

Yes, basically.

It links the refresco to the masa madre:

• the refreshment of the starter
• the starter’s refreshment/feeding

So the structure is:

• el refresco = the refreshment/feeding
• de la masa madre = of the sourdough starter

Together: the sourdough starter’s refreshment/feeding

Yes, it is grammatically correct and understandable, especially in a baking context.

That said, depending on exactly what you mean, native speakers might also say things like:

• Dejamos de comprobar el refresco de la masa madre
• Dejamos de vigilar el refresco de la masa madre
• Dejamos de controlar la masa madre
• Dejamos de alimentar la masa madre

The difference is subtle:

• revisar el refresco = check the refresh/feed
• alimentar la masa madre = feed the starter

So your sentence sounds more like we stopped checking the starter’s refreshment/feeding, not necessarily we stopped feeding it.

The sentence breaks down like this:

• Dejamos de revisar = we stop / stopped checking
• el refresco = the refreshment / feeding
• de la masa madre = of the sourdough starter

So the overall structure is:

[verb phrase] + [direct object] + [de phrase]

More specifically:

• Dejamos de revisar = verbal expression
• el refresco de la masa madre = the thing being checked

That makes el refresco de la masa madre the direct object of revisar.