"I love him, because he has sisu."
Translation:Rakastan häntä, koska hänellä on sisua.
It's probably DL that is confusing you because it's still in beta and it sometimes accept phrases without the pronoun and sometimes not even when they could very well be written without it. The basic rule is that you can omit the 1st and 2nd person pronouns, both singular and plural (minä, sinä; me, te); but you cannot omit the 3rd person pronouns (hän, he). Every time DL tells you something else about 1st and 2nd person pronouns, just report them as missing translations because they both should both be accepted as correct.