I always considered the form て+いる as the expression of an ongoing action, but recently I read an article that it can be read as succession of the て form verb and the verb いる. Then, 'もう、家に帰っている。' would not mean 'I am already coming back to my house'. It would mean 'I am already home (I've gone home and I am waiting there now)'. Is it true? When do I know which translation should I use? Are there any possible translations? How I use them?

Thanks in advance.