Does the location matter in a PhD choice?
I do not want to quit my second PhD.

It would be unfortunate if you needed to quit -- but not the end of the world.

I want to start a new PhD being sure of what I am doing.

In my experience, it is rare to ever be completely sure of what you are doing.

How much social life and location can make a difference in your life?

A lot.

What should I do?

Ultimately, only you can say.
That said, you've already accepted an offer in Sweden. You're very happy with the university, and apparently your boyfriend is there. In your shoes, personally, I would go and try to make the best of the situation. It won't be for the rest of your life, and if things go badly then you can reevaluate later.