"I love you."
Translation:Jeg elsker dig.
It can also be used to describe love for an object or band (though I would definitely be careful saying it about friends, in case it can get misinterpreted, but I wouldn't say you can't full stop). It can also be used to describe actions you love doing.
"Jeg elsker chokoladekage" = I love chocolate cake
"Jeg elsker at spise chokoladekage" = I love to eat chocolate cake
I'm not sure about this, but how I figured it out is figure out if you would say me(mig) or I(jeg). Du would be like I and Dig is like me. You wouldn't say I love I in English, you would say I love me. Therefore, in Danish, you would say Dig. Hope this helped! It does take a bit of practice and just reading and listening to more Danish.