1- Is that the way to go, to let the second transaction be confirmed?
Base in my own experienced if your first transaction still not confirm your 2nd transaction will not confirm you should wait first(parent) transaction to be confirm your transaction will be confirm sooner.. If you send this transaction just few hours ago your transaction could be long time to confirm due to high traffic from the network look at the fee
https://bitcoinfees.earn.com/The transaction fee is getting high every hour that i think there are lots of transaction right now are having the same thing or stuck transaction..
2- Is there a tutorial about manually editing the local ELectrum files, in order to prevent the wallet to re-send the transaction forever?
No you don't need to edit any files and electrum will not resend any bitcoin its all manually..
The only thing that i know is to submit your parent transaction to free accelerator if you don't want to pay here
https://www.antpool.com/user/prioritiseTransaction.htm?m=savePrioritiseTxJust register and go to in that page and submit your parent transaction.. And hope for 1 day to confirm your transaction..
Or hire miners to confirm your transaction there are some paid services to accelerate transaction.