- "I'm at work" OR "I'm at the office". If you want to be more specific you could say "I'm at my desk" OR "I'm in my office" (referring to your own private room at your workplace).

 

- "I'm on the phone/computer" and "They're showing the game on TV tonight".

 

- "I was at home in my room on the computer at 10:00pm".

 

Prepositions can be tricky. You can find some good examples of how to use them at the following links:

 

1) http://esl.about.com/library/beginnercourse/bl_beginner_course_gr_prep1.htm

2) http://esl.about.com/od/grammarintermediate/a/prepositions_of_movement.htm 

3) http://www.talkenglish.com/Grammar/prepositions-on-at-in.aspx

Hi Jesse, It's hard to tell the context in which you are saying these sentences, but I would say them like this: 1) "Can you help me by correcting this sentence?" or simply "Can you correct this sentence?" 2) "Spoon-feeding children stifles their creativity. It is also a waste of time." In general, I would use the word "additionally" to start a sentence rather than "in addition to this". Other ways to say the same thing include "also", "moreover" and "furthermore". Don't worry, you're doing great! Making mistakes is perfectly normal - even us native speakers constantly make mistakes :)