Dortmund is publicly listed, negotiations with those kinds of clubs are done differently. Any real offer made would have to be publicly disclosed by Dortmund, which the club certainly do not want. Because of that its just tons of discussions and sounding out through intermediates, because you only want to make an official offer, once you are absolutely sure it will be accepted. Since Dortmund appear to be adamant about keeping him, the club probably will never make an offer this summer. Which does not mean they didnt try everything.