It is OK to use close vicinity but the phrase is a little redundant and there are better ways to express proximity to. Use, "near, next to, adjacent to, in the vicinity of", etc. Set up your phrase like this: In the vicinity of the shopping mall, close to the entrance. I will meet you there. Better sentence structure and proper that way.
it is not correct English, you rather say still
It is correct.
It would be more correct to say, someone who.
It is correct English to say decent skill but not decent ability
It is correct English to say "He went off on a tangent".
no it is not correct to say you are not for sure instead you can say in proper English that you are not sure about something
No. In English we say "How old are you?"
Yes, it is correct to say out of compliance with. It means out of help with in English grammar.
No, it is not proper English to say "on tomorrow." The correct phrase is "tomorrow."
no you should say "Did you get an A on the English exam?"
In American English we say My family is; in British English we may say My family are.
It is not correct English to say "somebody has learned something from an early age" due to the use of "has".