Nice to meet you

Hi,I'm Mizuki.

I've been started studing English for a month ago.

Hello Mizuki, nice to meet you too.

You have mixed up 2 messages! You can either say 'I started studying a month ago.' or 'I have been studying for a month.' There is very little difference in meaning but he first one is focused on the action of starting and the second on the length of time you have been studying.

Hope this helps

Bob

Hi,I'm Mizuki.

Nice to meet you

I've started studing English a month ago.