Nos arriesgamos en el juego cooperativo.

Nos is the first-person plural reflexive/pronominal pronoun, so it goes with we.
In nos arriesgamos, it does not translate word-for-word as ourselves in natural English. Instead, the whole expression arriesgarse means to take a risk or to put oneself at risk.

So nos arriesgamos is understood as we take risks / we risk it.

It is often better described as a pronominal verb.

There are two related patterns:

• arriesgar algo = to risk something
  
  • Arriesgamos mucho dinero = We risk a lot of money
• arriesgarse = to take a risk / to put oneself at risk
  
  • Nos arriesgamos = We take risks

So in this sentence, the verb is being used in its pronominal form: arriesgarse.

By itself, arriesgamos can be either:

• present: we take risks
• preterite: we took risks

That is because the nosotros form of many -ar verbs looks the same in those two tenses.

So this sentence is grammatically ambiguous in isolation. Context tells you which meaning is intended.

With a conjugated verb, object and reflexive pronouns normally go before the verb:

• Nos arriesgamos

That is the standard placement.

You only attach the pronoun to the end in forms like:

• arriesgarnos = infinitive
• arriesgándonos = gerund
• arriesgaos = affirmative vosotros command

But with a normal present-tense or past-tense finite verb, nos goes before it.

Here en means in or within the context of the cooperative game.

So en el juego cooperativo means something like:

• in the cooperative game
• in co-op play
• when playing the cooperative game

Other prepositions would change the meaning:

• durante el juego cooperativo = during the cooperative game
  more focused on time
• a el juego cooperativo would be wrong here

So en is the natural choice for the setting or context.

Spanish often uses the definite article el/la/los/las where English may or may not use the.

Here, el juego cooperativo suggests a specific known game or a specific cooperative mode/context.

• en el juego cooperativo = in the cooperative game

If you remove the article, en juego cooperativo, it sounds more like a label or category, and is less neutral in a normal sentence.

Yes. Juego cooperativo is a normal way to say co-op game or cooperative game.

Depending on the context, Spanish might also use:

• modo cooperativo = co-op mode
• jugar en cooperativo = to play co-op

So if you are talking about the game itself, juego cooperativo is fine. If you are talking about a mode inside a game, modo cooperativo may be more precise.

In Spanish, descriptive adjectives usually come after the noun.

So the normal order is:

• juego cooperativo

not:

• cooperativo juego

Putting the adjective first is usually either impossible, very unusual, or stylistically marked. For a basic descriptive phrase, noun + adjective is the standard pattern.

Yes. Spanish word order is often more flexible than English word order.

For example, you can also say:

• En el juego cooperativo nos arriesgamos.

That still means the same thing, but it puts more emphasis on the setting: in the cooperative game.

The original order is perfectly natural too:

• Nos arriesgamos en el juego cooperativo.

Arriesgamos has a strong rolled or trilled r sound because of the rr.

Very roughly:

• a-rries-GA-mos

The rr is written because a single r between vowels would normally sound softer.

So:

• caro = soft r
• carro = strong rr

The same idea applies in arriesgamos.