Is easy to use, but It accept only char for twitting
This is not true. It posts arrays of characters, not single characters.
i'm able to compose texts and sensors values only with string.
Again, not true. There are ways to create character arrays containing data from sensors.
A string (lower case s) is simply a NULL terminated array of characters.
A String (upper case s), on the other hand, is a poorly written wrapper around the string concept.
A string (multiple characters) can not be converted, meaningfully, to a char (a single character).
Post your code, so we can help you choose the appropriate data type and formatting functions.