Learn Hardcore Esperanto: En nia teamo afabla respondo ofte helpas pli ol laŭta respondo. - In our team a kind answer often helps more than a loud answer.

En nia teamo means in our team. It sets the context first, like saying as far as our team is concerned or within our team. Esperanto often puts this kind of context phrase at the start, but it could appear elsewhere too.

Why is it nia teamo, not nian teamon?

Because en is a preposition, and after a preposition Esperanto normally does not use the accusative -n for simple location.

So:

en nia teamo = in our team
nian teamon would not fit here

A useful contrast is:

en la domo = in the house
en la domon = into the house (direction/movement)

Here there is no movement, just location or context.

Why do afabla and laŭta end in -a?

Because they are adjectives. In Esperanto, adjectives always end in -a.

afabla = kind
laŭta = loud
respondo = response

Adjectives also agree with the noun they describe. Since respondo is singular and has no -n, the adjectives stay in the basic form too:

afabla respondo
laŭta respondo

Why is there no word for or ?