Всё таки медаль была выиграна до того, как мама о ней рассказала. По согласованию времён здесь должен быть Perfect.

Ольга, да. Здесь должно быть: Mother said that we HAD won the gold medal in judo.

Артикль нужен. И "gold medal", а не "golden medal".

Olga and Galina, the use of which perfect depends on when the statement is uttered, i.e. in the present or the past. If you're remembering the summer of 1975, you could say: "That morning, Mom told us that we had won the gold medal in judo." -or- "By the third day of the Olympics, we had already won the gold medal in judo." But if you're speaking in the present, you say: Mom said we won the gold medal in judo." If you consider this a great victory for your country, you can turn it into an "announcement" by using the perfect to emphasize it as such: We've won the gold medal in judo!"

Also, you just say "we took the gold in ..." https://www.google.com/#q=%22US+took+the+gold+in%22

Улий, спасибо большое! А я как раз сегодня подумала, что в этой фразе могут быть варианты, и собиралась об этом написать, but you beat me to it. ))

Галина, всегда пожалуйста!