Ответ:
У тебя везде одна общая ошибка. Я также поменяла немного предложения, что бы не было тавтологии. В первой части твои предложения, во второй- мои варианты
Объяснения
In this project I want to talk about the seven wonders of Russia= I want to talk about 7 Russian`s wonders in this project.
The first wonder of Russia that I chose is Lake Baikal= Lake Baikal is the first wonder I`ve chosen
The second wonder of Russia that I chose is Valley of Geysers= Valley of Geysers is the second wonder I want to talk about
The third wonder of Russia that I chose is Mamayev Kurgan= Mamayev Kurgan is the third fantastic wonder
The fourth wonder of Russia that I chose is Peterhof= Peterhof is the fourth Russian`s wonder
The fifth wonder of Russia that I chose is Saint Basil"s Cathedral= Saint Basil"s Cathedralis №5 in my top-list
The sixth wonder of Russia that I chose is Manpupuner rock formations= Manpupuner rock formations is the sixth wonder I want to talk about
The seventh wonder of Russia that I chose is Mount Elbrus= Mountain Elbrus is the seventh wonder
Всем удачи и добра!!!