After completing the three subquests in Kaer Morhen, the next part of the storyline will be presented in the form of a cutscene. Dialogue options won't matter: if you want to speed things up, don't agree on any witchers' propositions, otherwise you will see many interesting and funny scenes. In one of them, after an alcohol libation, you will have to find Eskel. You will find some wine marks with witcher senses, they will lead you to the half-conscious witcher. You can optionally play Gwent with the witchers, but you won't receive cards for that.
Next day you will start another part of the quest - you must prepare a potion. Yennefer will give you the receipt. Walk to the table nearby and take all ingredients from the container. Now open the alchemy panel and prepare the potion from the last category related to quests. Take the potion to the sorceress. After another cutscene you will receive new quest - once again, you return to Skellige. Next quest is called The Isle of Mists.