"Kami berjalan."

Translation: We walk.

[JarrodMain]

berjalan = to travel
berjalan kaki = to travel by foot (walk)

[helpme388906]

what is the difference between 'kami jalan' and 'kami berjalan'?

[aarspar]

"Kami jalan" is informal, while "kami berjalan" is formal.

[Karel328342]

Kami berjalan - We walk. Can be "We go"? Because I mean, walk = jalan kaki.

[Rick392366]

"We go." = "Kami pergi."

[Mark436414]

Is the prefix "ber" used primarily with intransitive verbs?

[Rick392366]

"ber-" + [base word] = intransitive verb.

"ber-" verbs are intransitive.
The base word can be a noun/adjective/etc...

[PepitaBebek]

Is "saya jalan" I walk (present simple) and "saya berjalan" I'm walking (present continuous)?

[aarspar]

No, they're not. To mark continuous aspect we use "sedang", thus "I walk" is "saya berjalan" (just saya jalan is informal) and "I'm walking" is "saya sedang berjalan". Indonesian doesn't usually mark continuous aspect unless necessary.