i wonder about privatekeys website
when i check for any addresss , i get the same addresses from different networks bitcoin gold , bitcoin cash ,,,etc
that has the same private key

?
and i wonder how is that possible without knowing the private key from the beginning ??
Never use such websites to search for your address/private keys, they will log and then will take any coin deposited to your address in the future.
Whoever holds the private key for puzzle 66, can spend all those garbage coins as well. You can even fork bitcoin and send millions of useless and worthless coins to that address.
Anyways, as long as a crypto coin is using secp256k1 curve to generate their private keys, all keys can spend from other coins which are using the same curve.
Ps, welcome Dr.😉