Η κάλυψη δικτύου και η ταχύτητα σύνδεσης είναι καλές εδώ.

A word-by-word breakdown is:

• Η = the (feminine singular)
• κάλυψη = coverage
• δικτύου = of network / network
• και = and
• η = the again
• ταχύτητα = speed
• σύνδεσης = of connection / connection
• είναι = is / are
• καλές = good (feminine plural)
• εδώ = here

So the structure is roughly:

The network coverage and the connection speed are good here.

Because there are two separate nouns:

• η κάλυψη
• η ταχύτητα

In Greek, when two definite nouns are joined by και, it is very common and natural to repeat the article with each noun.

So:

• η κάλυψη και η ταχύτητα = the coverage and the speed

This sounds more complete and standard than leaving the second article out.

δικτύου is the genitive singular form of το δίκτυο (the network).

Greek often uses the genitive where English uses of:

• κάλυψη δικτύου = coverage of a network / network coverage

So δικτύου is not the basic dictionary form; it is the form needed after κάλυψη to show the relationship.

For the same reason as δικτύου.

• η σύνδεση = the connection
• της σύνδεσης = of the connection
• σύνδεσης can appear without the article in a phrase like ταχύτητα σύνδεσης

So:

• ταχύτητα σύνδεσης = connection speed / speed of connection

Greek often builds noun combinations this way, using the genitive.

Because the subject is actually two things joined together:

• η κάλυψη δικτύου
• η ταχύτητα σύνδεσης

Together, they make a plural subject, so in English we say are good.

In Greek, the form είναι is used for both he/she/it is and they are, so the verb itself does not change here:

• είναι = is
• είναι = are

You understand the number from the subject, not from a different verb form.

Because it describes two feminine singular nouns together, which makes the overall subject plural:

• η κάλυψη = feminine singular
• η ταχύτητα = feminine singular

So the adjective must agree with the combined subject, and that becomes feminine plural:

• singular feminine: καλή
• plural feminine: καλές

That is why Greek says:

• Η κάλυψη ... και η ταχύτητα ... είναι καλές

In standard Greek, no.

Since the sentence has a compound subject joined by και, the adjective should be plural:

• είναι καλές = are good

Using καλή would only work if you were talking about just one feminine singular noun, for example:

• Η κάλυψη είναι καλή. = The coverage is good.
• Η ταχύτητα είναι καλή. = The speed is good.

But with both together, καλές is the correct form.

Because both nouns are feminine:

• η κάλυψη = feminine
• η ταχύτητα = feminine

When Greek adjectives describe multiple nouns of the same gender, they usually agree with that gender in the plural.

So:

• feminine plural = καλές

If the nouns were neuter, you would use καλά.
If they were masculine, you would use καλοί.

Greek word order is fairly flexible, and adverbs like εδώ (here) often come at the end.

So this is very natural:

• Η κάλυψη δικτύου και η ταχύτητα σύνδεσης είναι καλές εδώ.

Placing εδώ at the end gives it a nice, natural sentence flow.

You could also hear other orders depending on emphasis, such as:

• Εδώ η κάλυψη δικτύου και η ταχύτητα σύνδεσης είναι καλές.

But the original version sounds very normal.

Yes, but the meaning becomes a bit more specific.

• κάλυψη δικτύου = network coverage in a general or label-like sense
• κάλυψη του δικτύου = the coverage of the network, referring to a more specific network

Likewise:

• ταχύτητα σύνδεσης = connection speed
• ταχύτητα της σύνδεσης = the speed of the connection

In technical or everyday informational language, Greek often prefers the shorter article-less genitive phrase, especially for general concepts.

Yes, it sounds natural, especially in contexts like mobile service, Wi‑Fi, internet quality, or a review of a place.

It has a slightly informational or neutral tone, like something you might say when evaluating service quality:

• The network coverage and connection speed are good here.

A Greek speaker might also say similar versions such as:

• Το σήμα και η ταχύτητα είναι καλά εδώ.
• Η κάλυψη και η ταχύτητα είναι καλές εδώ.

But your sentence is perfectly natural and clear.

A rough pronunciation guide is:

ee KÁ-lee-psee dheek-TÝ-ou kee ee ta-HÝ-tee-ta SÝN-dhe-sees Í-ne ka-LÉS e-DHÓ

A few helpful notes:

• η sounds like ee
• κάλυψη has the stress on ΚΑ
• δικτύου has the stress on ΤΥ
• ταχύτητα has the stress on ΧΥ
• σύνδεσης has the stress on ΣΥΝ
• καλές has the stress on the last syllable
• εδώ also has final stress

The stress marks in Greek are important and should be pronounced clearly.