The problem may be with the export from MyHeritage.
There does not seem to be an option for choosing the character code set when you export from MyHeritage (I just checked). As far as I know, it should be UTF-8.
Long ago, when I had decided to close my paid account with MyHeritage I exported what I had there - and all my dear Swedish Å-å-Ä-ä-Ö-ö characters were mangled.