Is SHA-256 safe and difficult to crack?
SHA-256 is a relatively poor way to store passwords but it is considered to be pretty much impossible to "crack". That is, retrieve the original plaintext from the hash.  

The reason it is poor to use for passwords, especially without a salt, is due to the fact that it is inexpensive to compute, thus more vulnerable to brute force and rainbow tables etc.

You won't be able to crack the hash you have been provided with.

If your question is about how to securely hash passwords, consider something like PBKDF2 if you still want to use SHA256 underneath.