"The participant reads his first newspaper."
Translation:Der Teilnehmer liest seine erste Zeitung.
It would be absolutely wonderful if the gender was put in the hint with nouns. This would help us to remember if the noun is m/f/n and by selecting the correct the correct das, die, der or what have you we would be better planing the gender in our heads with the word. Because quite honestly this guessing is not achieving what I believe is their goal of teaching me German in a pleasant and effective manner.
Ok, so basically, possessive articles, and attribute adjectives do not change in the same way, they don't get the same endings. But, they do become qualified by the noun they are describing For instance, "Das ist mein erste Hund". Grammatically, is that right? The way I see it is that we have "der Hund" in the nominative case, and therefore, the possessive article "mein" is used, and the weak inflection of the attributive adjective is used - erste -....
ihm is the dative form of the personal pronoun es - it means "to him", or other indirect object usages.
The possessive pronoun "his" = sein and its declensions, in this case seine because (die) Zeitung is feminine singular accusative.