Assume that attacker only could obtain ciphertext, but knows that method is symmetric. Is there a way to find which algorithm was used for the encrytion?
And in general, if attacker knows the encryption method, is it helpful for the process of breaking or decryption?
What types of breaking process is there in this situation?
If the attacker knows the encryption method, then assuming it's a decent algorithm it won't help them break the cipher in any meaningful way. Cryptography is designed and analyzed under the assumption that the attacker knows everything except the key; among other reasons, it's incredibly hard to keep the attacker from knowing the system, while a key is much easier to keep secret.
What you describe (figuring out which cipher was used, given only the ciphertext) is a type of distinguishing attack. Modern ciphers are generally highly resistant to such attacks: the ideal cipher produces output that is indistinguishable from random noise.
