Unit 7

Could you correct me, please?

Students are not allowed to run along school corridors.(corridors tiene sentido, pero "hallways" es más común)
Few people choose to spend their time taking exercise exercising.
The internet means that we spend more time sitting at home, but we cannot imagine living without it.
Being fit and healthy does not (o, doesn't) mean running 20km a day.
Many students would prefer to cycle (en EEUU decimos "bike" en lugar de "cycle") to school than going go by school bus.
Many people only think about taking exercise exercising when they are overweight.
Unless they try to compete as a team, they will not succeed to win the competition.
Doing sport Playing sports is a good alternative if you´re bored to sit and read a book. to sitting and reading a book if you're bored.
It may be good using a bicycle to bike/ to ride a bike instead of going by public transport.
There are several good reasons to ride a bike.
I didn't help not to laugh at his effort (No estoy seguro lo que estas diciendo aquí. "I couldn't help but laugh at his effort" tal vez?)
Cyclists can't use the pavement. (banqueta en EEUU = "sidewalk)
Mateo succeeded to win the race. won the race/ managed to win the race.
Tanya didn't find difficulty it difficult to learn to windsurf.

This is very well written. I made a few corrections that sound more natural to a native speaker. Don't hesitate to write me if you have any more questions. Esto es bien escrito. Hice varias correcciones que suena mejor a un hablante nativo. No dudes en contactarme si tienes más preguntas.