Could you explain to me when I should use the V-masu form and when the V-ru form?
If I meet someone for the first time, which form should I use? Is it impolite to use V-ru form when I talk to someone older?
The v-masu form is the polite one, and it's the one you should use when you meet somebody (older or same age) for the first time.
The V-ru form can be used when talking to somebody you are close to: for example, friends.
i agree with both of them but what my sense s have told me its if your going to japan and you dont raly know haw to say it in a formal way and you dont seam to be japanes they would understand why you are talking to them on an informal way if you say first that japanes its not your first language therefore you cant speak it perfectly
joust remember if you also speak the inpilite form with a polite tone of voice it wont be than inpolite more it your betwen ages in 10 to 18
That's right, it is more polite to use the -masu form, not only with the people you just met, but with everyone you are not too close yet.
You could use the -ru form if you don't know how to use the -masu and japanese people might understand you, but remember that they are very polite people, so if you try and use the -masu form they will appreciate it.