I also tried to import my private key into the electrum wallet, but also this did not work as I wished.
What happened during import?
Because that should work except if you're using P2SH-P2PK addresses instead of P2PKH.
For the full export and import guide, read this post by HCP:
/index.php?topic=4746784.msg43255691#msg43255691Import or Sweep tutorial to Electrum is posted 4 posts below it.
I only recommend doing this as your last resort though.