decryption many time pad I have eleven ciphertexts that were encrypted with the same key (which I don't know). I want to decrypt the last ciphertext. I read similar question like Many time pad attack but I can't solve my problem with their answer.

I'm new in Crypto can anyone tell what can I do?

I know when XOR two ciphertext (Let's assume that the plaintexts consist only of spaces and ASCII letters) if both of them were space the result is null. If one of them was space and another was ASCII we have a new ciphertext. If both of them were ciphertext we have new word that is XOR of orginal message but how can I reveal the plain-text?
This sounds suspiciously like the first extra credit assignment out of Dan Boneh's Cryptography I on Coursera.  Dan gives you a great hint in the assignment listing for this one.  Take a look at an ASCII chart and note what happens when you XOR something with space rather than with an alphanumeric.

Once you've got that sorted out, your best bet is to XOR things together, as you suggest, and use the knowledge gained from Dan's hint on XORing with space to build a histogram of candidate plaintext characters for each position.  My first cut at this assignment got about 85% of the characters, and filling in the rest was simple due to the common digraphs of english.