The
echo "invalid characters like Å, å, Ä, ä or"
is providing the input data with illegal characters that need removal. I need some test data and this is one way to demo a command. And the command I am showing is
tr -dc " a-zA-Z0-9,\n"
and that is what removes the garbage. The tr command, in this form, lists the valid characters, not the invalid ones. You may need to add stuff to the list. To replace invalid characters with a space use

$ echo "invalid characters like Å, å, Ä, ä or"| tr -c ' a-zA-Z0-9,\n'  ' '
invalid characters like  ,  ,  ,   or
$

tr -c ' a-zA-Z0-9,\n'  ' ' < inputfile > outputfile