Unknown

I have a problem. My girlfriend has a twinflame. Every time we have sex, then I cannot go 100% for her because if we do it then I always think that she thinks of him than of me. What am I doing about this?

b
There is nothing you can do about it. You cannot send her twinflame away, nor can she. It is up to you whether you want to continue with her. Stay strong.
(Arundash)

Answer 2
Perhaps it will reassure you a little when I speak from my experience that when I am physically intimate, I am busy with the physical partner and not with my Twin.
(Unknown)

Answer 3
I agree with answer 1. If it really is a twinflame, then you cannot do anything about it. Hopefully for you, your girlfriend has not had a physical relationship with her twinflame, because other than it is a matter of time I am afraid.
(Antoon)