No, they’re not the same. I think there are different IPAs for each language. From https://en.wikipedia.org/wiki/Voiced_dental_fricative: “Danish [ð] is actually a weak, velarized alveolar approximant.” That is, an approximant of the voiced dental fricative, which is written [ð] in the English IPA.
Labas, Laima! You have the problems because in LT you don't have this sound at all... If you've heard Latvian L or the Polish hard L it is somewhere a bit similar. Only you put your tongue against your lower teeth and make the sound like you were a bit sick or didn't like smth. Did it help?