Arrreeeeeeeee????!!!!

Ok.
So, in two weeks my japanese has improved more or less...let me see... sugar loads.
I think I have added a good bunch of words to my regular vocab, and I also started to make sentences. Thank you WORK at a coffee shop with nice people and nice customer and nice music and nice tea and good humour.

But can ANYBODY explain to me how on earth this is possible:
there's this dude at work, whose Japanese I simply cannot understand to save my life because:

1. he never went abroad and doesn't understand using simple japanese would help me
2. I think he uses loads of slang words I never heard of
3. he talks fast
4. I just don't understand him

Well, we took a walk through the park, and you know what we managed to talk about, me and my tiny little bit of japanese and his five single sorry words of English?
No, not the weather, not music, none of those flipping EASY subject NORMAL people talk about when they don't happen to speak the same language.
No.
No, we talked about god, and the non existence of god, the big bang, the creation of the universe, fucked up childhood on his part, fuck up childhood on my part, the ridiculous habit the japanese people have here of dressing their dogs with pyjamas, the reasons why some people don't want children, depression, friendship, and forgiveness.

Anyone explains to me how this happened wins a mars bar.