Hi Funambola. Welcome to BPDR! I'm Harmonium, and I'm pretty new around here too, although I visit often.
We don't know each other very well yet and I'm not trying to assume anything about you or your situation. I'm going to just give you my thoughts based on your post. Your English is fantastic, by the way. I studied German in high school, but there is no way I could converse in your language the way you can in mine. I'm impressed!
For me, Radical Acceptance doesn't mean I have to like a situation. It just means that I have to 'accept' the reality of the way things ARE. It sounds to me like you are facing that kind of delima. Your bf broke things off and has now moved on, but you have also made some changes and would like a second chance. Is that right? If so, IMHO, Radical Acceptance would be accepting that you and your bf are no longer together. That would involve you trying to find a way to be happy in your life without him. Not necessarily being happy about that turn of events, but realizing it is what it is. What better way to demonstrate to yourself and others that you are no longer obsessive than to move on?
I hear you saying that you want to be happy for him but it hurts you to do so because you still have feelings for him. I sympathize with your situation as I understand it--I have been there before myself. Many of us have. Letting go of someone we care for can be a very difficult thing to do. It helps me to know that a certain amount of 'grieving' for the relationship can be a very normal thing. It's getting stuck in that grieving stage I try to avoid.
Have you read the Tool section on the left upper hand of your screen? I think maybe the
five steps could help you identify a good direction for you to go with this problem. I have found that tool to be particularly helpful.
Best wishes to you!