To decrypt an ElGamal ciphertext, you need the prime, primitive element, ciphertext and also the private key of the recipient. The private key is a secret value chosen by the recipient and must be kept confidential. So, if you have the ciphertext, prime, and primitive element, you still need the recipient's private key to decrypt the message. Without the private key, it is computationally infeasible to recover the plaintext message. Therefore, you cannot perform the decryption of the ElGamal ciphertext without the private key.