"Like" in this case means "as if". To be more clear: As if you haven't already done enough. This is sarcasm. The person is saying that the person has already contributed negatively to the situation and that they would like them to stop before they make the situation worse. Like has many meanings in English.

Like isn't a filler word here. (It is often, but not here).

"Like" in this case is a filler word. It's used by young people and it sounds ridiculous. There was a good discussion on this a few days ago. You shouldn't use it. Also, "Friends" is popular for many to learn English. It's probably one of the worst resources to use.