"doch mal" = 1. you have never done it before (and actually you didn't want to do it first) but then you are doing it --> "okay, actually I didn't want to try on the jacket. But it suits you so well that I also want to try it" "doch mal" = 2. as a kind of a friendly push --> "Probiere die Jacke doch mal" = "come on, try it on- maybe it suits you" "nochmal" = again --> you tried the jacket once and now you will try it on a second time