Goodbye to 'By'
By paying more attention to corruption can improve the welfare of a country.
🇮🇩
Yet another Indonesian structure that doesn't translate directly into English!
If you really must begin with 'by' then you need...
By + [name of solution] + comma + subject + verb (+ etc)
By paying more attention to corruption, a government can improve the welfare of a country.
However, native speakers would probably just say "Goodbye to 'By'" and go straight to the solution as the theme in the sentence:
Paying more attention to corruption can improve the welfare of a country.