Learn Turkish: Atıkları sokağa attığı için çevreye zarar veriyor. - He is harming the environment because he throws the waste on the street.

This uses the grammar structure you're learning now! It combines the verb atmak (to throw) with the -dık suffix (which changes to -tık here) and the 3rd-person possessive ending -ı. Literally, it means "for his throwing." In Turkish, this is how we connect a verb to için to say "because he throws" or "because he threw."

Why is there a ğ in sokağa?

The root word is sokak (street). When we add the dative suffix -a to mean "to the street," the hard k at the end of the word softens to a ğ because it is now between two vowels. This is a common consonant mutation in Turkish that you learned in earlier lessons.

Why does "harming the environment" translate as çevreye zarar veriyor instead of just using çevreyi?

In Turkish, to harm something is expressed as zarar vermek, which literally means "to give harm." You give harm to something, so the target of the harm takes the dative (direction) case. That's why çevre (environment) gets the -ye suffix, meaning "to the environment."

Why does the sentence use atıkları instead of just atıklar?