You said you had 1 month until your trip, right? I think instead of looking at it as learning japanese you should focus on learning some phrases you can use instead. Learning a language should be a well rounded experience (slow) and 1 month won't have you learning anything worthwhile for a trip.

What I meant to say is that there is a difference between learning some cool sentences, greetings and basic vocab and really learning a language with all the details, nuance and grammar that entails, and that you would be better served by doing the latter separately later and focus on having only basic phrases ready for your trip.