how to propose to getting marriage?

The question will be: would she be surprised at all? If you already have a daughter with her, it must be already a long time ago that she "expected" you to marry her. And if you have not asked her to marriage, doing it now may not give her a reaction of disbelief, not surprise? That may not be a happy surprise for getting what she expected during the time she expected it. If that expectation already lapsed, there may be no way of surprising her anymore. Only you will know what's the real situation of course. I guess it is no longer time to surprise her. It has been time you should have married her.

proposing of getting married the common used here is giving of a rin as a simble that you are engaged with a man that watever happen you will find another man. Proposing a marriage should have a good planning and a good start the successful to enter in this relationship are those capable to do so and is ready to accept responsibility as a future father.