El geocacher va y pierde el mapa sin conexión.

Not literally. Ir y + verb is a common colloquial Spanish pattern used to show surprise, annoyance, disbelief, or emphasis.

So El geocacher va y pierde el mapa sin conexión means something like:

The geocacher goes and loses the offline map.

In English, goes and loses also has that feeling of and then, stupidly / unexpectedly, he loses it. If you remove va y, the sentence becomes more neutral:

El geocacher pierde el mapa sin conexión.

Spanish often uses the present tense to describe something vividly, as if it is happening in front of you. This is sometimes called the historical present or narrative present.

So va y pierde can sound more immediate and dramatic than a plain past tense.

If you wanted to tell it as a past event, you could say:

El geocacher fue y perdió el mapa sin conexión.

or simply:

El geocacher perdió el mapa sin conexión.

Because perder is a stem-changing verb. In many present-tense forms, the e in the stem changes to ie when it is stressed.

So you get:

yo pierdo
tú pierdes
él/ella pierde

But:

nosotros perdemos
vosotros perdéis

This is a very common pattern in Spanish.

Because Spanish normally uses an article before a common noun when it is the subject of a sentence.

So el geocacher means the geocacher. If you were talking about an unspecified one, you would say un geocacher.

English sometimes drops articles in places where Spanish does not, but here Spanish needs one.

Geocacher is a borrowing from English. Spanish often keeps modern hobby or tech words in borrowed form, especially when there is no single widely used native equivalent.

It is masculine here because the sentence uses el. With borrowed nouns, Spanish very often defaults to masculine, especially when talking about a man or when using a generic form.

If you were clearly referring to a woman, many speakers would say la geocacher.

Because not all nouns ending in -a are feminine. Mapa is one of several words of Greek origin ending in -ma that are masculine.

Other common examples are:

el problema
el sistema
el tema
el programa

So the correct form is el mapa.

It means without connection, usually in the sense of without an internet connection or offline.

In this sentence, it most naturally refers to an offline map: a map you can use without being connected to the internet.

So el mapa sin conexión is basically the offline map.

After sin, Spanish very often leaves out the article when speaking in a general sense.

So:

sin conexión = without connection / with no connection

This is the normal, natural wording.

You would add an article only if you meant a specific connection:

sin la conexión del hotel = without the hotel’s connection

In this sentence, most people will understand sin conexión as describing el mapa: an offline map.

Still, the phrase can feel a little context-dependent. If you wanted to make it extra clear, you could say:

pierde el mapa offline
pierde el mapa que tenía descargado
pierde el mapa cuando está sin conexión

Those versions make the intended meaning more explicit.

Yes. Without va y, the sentence is grammatically fine:

El geocacher pierde el mapa sin conexión.

That version is more neutral and factual. Adding va y makes it more expressive and conversational, often with a slight feeling of frustration, irony, or disbelief.

Because it is a borrowed word, pronunciation can vary a bit. A Spanish-style pronunciation would be roughly:

je-o-ka-CHER

The final syllable is likely to be stressed if it is written exactly as geocacher, because Spanish stress rules normally stress the last syllable in a word ending in a consonant other than n or s.

Since it is an English borrowing, though, real-life pronunciation is not always fully standardized.