make an atmosphere, where your friends ,teachers speak only in English and you try to communicate with them.and I am sure after 1 or 2 month,you will be fluent and accurate speaker.

yes, going out for dinner is the right answer because when you are going somewhere. ..you should use 'for' ...

your sentence is correct. .but better way to Say the same is : if he is happy without me then I am more happy for him...

yes,you is the right answer to say tu ,tum,aap ... there is no other word to say aap in English....

obviously, 'addressing' is the correct one.....