Learn Hardcore Italian: Il commesso controlla le monete prima di restituire il resto. - The clerk checks the coins before giving the change.

In Italian controllare can mean both to control and to check/inspect. Here it means checks (verifies) the coins. You could also use synonyms like verificare or esaminare to convey the same idea of inspection.

Why is controlla in the simple present tense? Couldn’t Italian say “is checking” like English?

Italian normally uses the present indicative for both the simple‐present and the present‐continuous. So controlla can mean either checks or is checking, depending on context. If you really want to stress the continuous action, you can use the periphrastic form sta controllando (e.g. Il commesso sta controllando le monete).

Why does the sentence use the definite article le with monete instead of just saying monete?

In Italian you generally include the definite article before plural count nouns, even when English omits it. Here le monete literally means the coins, referring to the specific coins the customer has given. Omitting the article (controlla monete) would sound odd or overly generic.

What’s the difference between monete and soldi? Why do we talk about coins rather than money?

monete = coins (metal pieces, countable)
soldi = money in general (uncountable)
The shop assistant is checking the physical coins you handed over, so monete is precise. If you wanted to say "The assistant checks the money," you’d say controlla i soldi.

What exactly does resto mean in this context?

Here resto means the change (the remainder of the amount owed to the customer). Literally, restare = to remain, and resto = what remains. So restituire il resto = "give back the remainder" = "give back the change."

Why is it prima di restituire (with an infinitive) rather than prima che restituisca (with a subjunctive)?

When the subject of both verbs is the same (il commesso), Italian uses prima di + infinitive (restituire). If the subjects differ, you must use prima che + subjunctive.
Examples:

Same subject: Prima di mangiare, lavo le mani.
Different subjects: Prima che tu mangi, lavo le mani. (notice tu mangi → subjunctive tu mangi)

How could I replace le monete and il resto with pronouns to avoid repetition?

You can use direct‐object and indirect‐object pronouns together. For example:
Le controlla prima di restituirglielo.
Breakdown:

Le = replaces le monete (feminine plural)
glielo = gli (to him/her) + lo (the change)

So it literally means "He checks them before giving it back to him."

Is restituire an –isc– verb? How is it conjugated?

Yes, restituire belongs to the second subgroup of –ire verbs that insert –isc– in certain forms. Present indicative conjugation:

io restituisco
tu restituisci
lui/lei restituisce
noi restituiamo (no –isc–)
voi restituite (no –isc–)
loro restituiscono

Could the shop assistant be a woman? How would you say that?

Absolutely. To specify a female assistant you use commessa instead of commesso. The sentence becomes:
La commessa controlla le monete prima di restituire il resto.