When he explained to us everything, we stopped worrying
1) We need to plant trees
2) We need to reuse things
3) We need to clean the beaches up
4) We need to save water
5) We mustn't pollute water in rivers
6) We mustn't throw garbage on the ground
7) We mustn't cut down trees
8) We need to protect animals
9) We must turn the lights off when we go somewhere
10) We need to recycle old magazines
Sitting-с двумя t
I am watching - вместо are надо писать am
on TV- вместо in надо писать on
are ready - без get
They're
I'm
Ну как-то так...
Прости больше не вижу ошибок.