1)Why benzoic acid is soluble in NaOH?

2)Why HCl is insoluble in titration of benzoic acid and NaOH?

Benzoic is soluble in a solution of NaOH because the base forms the sodium salt with the acid to form sodium benzoate. The sodium salt is soluble.
The second part of your question isn't clear. Are you titrating the sodium salt? And HCl is soluble in most anything.