1. Used alone to mean that you will accept something as true or real, or try to do something that you doubt will work, only provisionally, as a kind of working hypothesis, in order to see what happens.
2. English = 'Okay, let's give it a go, then!', 'Let's see what happens then!', 'I'll try, but I don't think it will work!', 'Okay, let's assume it's the case', and so on.