I believe I have found the private keys though a python script but it is totally unreadable, meaning it is consisted of signs like squares, question marks, crosses etc.
How do I decrypt it to a standard private key?
Private keys are not saved in hex, and it is also very unlikely the key is unencrypted. The comment on this method explains how key data is serialized: https://github.com/goatpig/BitcoinArmory/blob/master/armoryengine/PyBtcAddress.py#L874
To decrypt a private key, you will need the following for each key:
InitVect (16 bytes) : Initialization vector for encryption
InitVectChk ( 4 bytes) : Checksum for IV
PrivKey (32 bytes) : Private key data (may be encrypted)
PrivKeyChk ( 4 bytes) : Checksum for private key data
as well as the KDF, packaged in the wallet header:
Crypto/KDF -- (512) information identifying the types and parameters
of encryption used to secure wallet, and key
stretching used to secure your passphrase.
Includes salt. (the breakdown of this field will
be described separately)
Assuming you can find the private key entry for the wallet root, you can ignore the rest of the wallet and reconstruct it from that one key.