I'm fairly certain видит is just "sees". If I wanted to say he was staring at her, I would probably say "смотрит" but I don't know if that's correct or not.
So the ending of all the subjects when are in accusative case change their endings to у?
Девочку sounds like Девочко on the audio. Am I missing something on the pronunciation?
When у isn't stressed, it may sound like о, and the same thing happens in English.
both mean (a/the) girl - but because of their case, they serve different functions in a sentence - and vice versa: because of their different functions, they have different cases. You determine function by the case, and you determine case by the function.