Complex sentence: She sent her daughter to Stockholm to have an operation that was promised to giver her eyesight back, but it failed, and Charlotta did not have the money to go back to Finland, and she had to stay in a boardinghouse for poor women.
Split into simpler sentences: She sent her daughter to Stockholm to have an operation that was promised to giver her eyesight back. But the operation failed, and Charlotta did not have the money to go back to Finland, and she had to stay in a boardinghouse for poor women.