strings in C++

Question

I have following questions regarding strings in C++:

1>> which is a better option(considering performance) and why?

1.

string a;
a = "hello!";

OR

2.

string *a;
a = new string("hello!");
...
delete(a);

2>>

string a;
a = "less"; 
a = "moreeeeeee"; 

how exactly memory management is handled in c++ when a bigger string is copied into a smaller string? Are c++ strings mutable?