DSL internet does not work

I'm using O2 DSL router since 2015 year and until last week everything was fine. Last Monday internet stopped to work. I do not speak German and had to ask my colleague to reach support by phone. We wasted around one hour (of course not for free, it will cost me ~25euros) and at the end were suggested to reboot the router and call from home again.
As I said I do not speak German, that's why I cannot call from home. And I don't want to waste more money trying to reach support.
Is there a way to help me and fix internet at my home? Or the only one solution for me is to cancel my contract (fortunately notice period "only" 3 months) and go to another provider?