I’m in the end of act 3 I think. But I can’t romance astarion

. I don’t know what I missed in the beginning that I didn’t get the right dialogue. So what did you do in the begging to romance him ?
Astarion's romance doesn't actually begin until part way through act 2. You have the option of sleeping with him in act 1, but this does not actually start the romance, rather it opens the option of romance later. In act 2 you have two options:
- speak to Araj Oblodra, the Drow blood alchemist in moonrise. You have to reinforce his decision to actually romance him, if you force him to bite her, it becomes unavailable. At the next long rest you should have a conversation with him that changes based on what your choice was, and if you reinforced his decision you can then start the actual romance.
- after completing the "Kill Raphael's old Enemy" quest by killing Yurgir, if his approval is high enough, at the next long rest you should be able to have a conversation where you can then start his actual romance.
I'm not sure if there's a way to start the romance in act 3 if it hasn't already begun.