'because she sleeps with me' -> 'because she sleeps at my place'?
'Den Abend kann ich wohl vergessen.' -> This means that the evening is ruined for him, literally 'I guess I can forget about the evening' - not sure how to translate it into English
'Kostet es auch teures Geld' -> 'Even if costs quite a bit of money', that's because of the word order, otherwise it would be 'Es kostet auch teures Geld'
'und lässt mich nicht ran.' -> (she doesn't agree to sleep with him) 'and doesn't put out' or something similar
These are the official lyrics, taken from the "die ärzte Songbook", only slightly reformatted.