"We have to play in a group."

Yep. It you typed that to translate from the English and got marked wrong, it simply means DuoLingo didn't consider that sense of the English translation.

Yes. And it makes more sense to play in a musical GROUP than to play sports in a group because in sports, the group is usually called a TEAM (un equipo). Context!

Yes, I reported it, you should too!

It should be translated:

In group - en grupo

In a group- en un grupo

In the group- en el grupo

The definite and indefinite article aren't used after the preposition en (and sometimes de) and the verb hablar. According to the book I'm reading.

Jugar y grupo, thought of a kids play group. Or just playing with more than a few people. But otherwise, I agree, playing sports would be team and equipo.

Yes, "tener que" = "have to"

Tengo que pagar la renta.

Tengo que ir al banco.

Tengo que salir a las nueve.

When you have something, then it's just "tengo"

Tengo hambre

Tengo ganas de leer

Tengo una mascota

I think "necesitar" is used for actual needs/necessities, such as "this plant needs watering" = "esta planta necesita que la rieguen" (got that example from spanishdict.com). The plant needs watering or it will die; if we don't play in a group, we'll be ok.

That would function in the same way (more or less), but it's not a literal translation of the sentence.

Hola Jim! "estamos" = we are............"tenemos" = we have

Hola learnTACO32: "Hemos" comes from "haber" and is only used as a helping verb to form the compound tenses like: "hemos llegado" we have arrived; "he escrito" I have written; "habían leído" they had written, etc. "Tenemos" comes from "tener" which means "to have" in the sense of "to possess". It can be used by itself: tengo = I have, tienes= you have etc. It can also be used in the phrase "to have to (do something)" such as, "Tengo que terminar mi tarea" I have to finish my homework. In this phrase it must be followed by "que" and the infinitive of the next verb. The "que" is not translated into English. This phrase has the sense of an obligation, something you must do. Make sense?

I believe this is the Spanish word "deber" and its conjugations.

You can say both, "en grupo" or "en un grupo", to my understanding there is no difference.

In an earlier post, someone shared this website showing that often Spanish omits the article when English uses it. I found it helpful and saved it, so here it is: http://spanish.about.com/od/adjectives/a/indefinite.htm

I know. DL keeps giving "he" in the drop down but rarely accepts it...???

You would need "que" after "tenemos".