Error Correction: Prepositions

1. On Saturdays, I go at the cinema to watch films and then get on a bus to visit my uncle.
   

2. I want go to the beach tomorrow. Come with me!
   

3. I work at two other people in a big office at the center of London where I can see at the river.
   

4. Every summer, I fly to Brazil and sit in the beach and look for all the beautiful girls who walk by me.
   

5. I go to shopping in Mario Supermarket in every Saturday.
   

6. I'm playing tennis in Sunday morning in 9 o'clock.