Wir haben projeden Tag viele Hausaufgaben.

With "pro", you would have to provide an exact figure of the number of homeworks.

Having said this - do you really have many different "homeworks“, or do you just want to express the idea of "a lot of homework"?

"a lot of" is expressed with the adverb "viel".

Normalerweise habe ich auf die Aktivitäten im Voraus geantwortet. (????)

Grammatically correct, but does not make sense in the context of this text. You are refering to specific "activities", but you didn't mention any activities before.

Also it is not clear how you can *answer* to something before it has happened; this is what "im Voraus" expresses.

Finally, I don't understand how you can "answer" an "activity".

Unsere Lehrerin empfiehlt uns eine Playlist, wo wir mit deutscher Musik hören können.

The "wo" is a bit odd. I don't listen ON a play list.

You could get it work, if you dropped the "hören": "... empfiehlt uns eine Playlist, wo deutsche Musik drauf ist". Still the "wo" sounds colloquial, since it could be written as "... Playlist, auf der deutsche Musik ist". But once you go so far, you can equally well get rid of the complete subordinate sentence and only supply an object group "Playlist mit deutscher Musik".

Sie hat gesagt, dass eine Musikstück pro Woche schon gut isausreicht/reicht/genügt.

"Musik" is not countable. It isn't in English either, right?

Am Wochenende werde ich auf die Aktivitäten bis Lektion 3 im Voraus antworten (?????).

Similar problem as before. You can answer a question, but not an activity. Also, what do you mean by "im Voraus"? And what "activities" are in the book?

Vergisst nicht, sdich auszuruhen.

Es dauert lange, zu antworten.

Vergisst nicht, sieuch auszuruhen.