Please note that importing your mnemonic code into another software wallet, does not transfer anything.
While you now have access to your coins via electrum, the private keys are still being derived from the original 12 worlds.
Now, i don't know anything about magnum wallet and neither did i ever hear from it. But i would recommend to create a new wallet with a new mnemonic code and move your funds over there.
If there has been a maliciously tampered random number generator (or maybe just a bug) in the wallet you have used to create your mnemonic code, your funds would be still at risk.
Dear bob123,
I did not use my 12 words. I opened a new electrum wallet, after that I have done "sweep" with using my private key with prefix "p2wpkh-p2sh:" to transfer my funds.
By choosing the Sweep method for transferring my funds to the new electrum wallet I have:
new mnemonic phrase
new private key
new address