在给定的一组句子中，找出正确的英语语法形式并解释差异。


1. I have been working here since 5 years.
2. I have been working here for 5 years.
3. I am working here from 5 years.
The correct English grammar form is the second sentence: "I have been working here for 5 years." 

This sentence uses the correct preposition "for" to indicate the length of time the action has been taking place. 

Sentence 1, "I have been working here since 5 years," is grammatically incorrect because "since" is used to talk about a specific point in time or event, but "5 years" is a duration, not a specific point in time. 

Finally, sentence 3, "I am working here from 5 years," is also grammatically incorrect because "from" is used to indicate the starting point of an action, but it doesn't provide information on how long the action has been going on, and "5 years" is still a duration.