Q: Is there way to change k1 visa to marrge visa in middle of it?

A: That seems unwise, but it depends upon your situation and relationship.

If you get married, then you will 'significantly delay processing' and be separated even longer. It is best for your fiance to come into the U.S. as a K1 fiance, so that you can both get to know each other better before marriage. The physical separation after marriage and I-130 processing has been known to create unnecessary emotional drama. It can also create challenges if you must take leave from employment to be with your spouse.

Ultimately, more separations upon a foreigner's admission into the U.S., and eventual divorces, seem to emerge due to prolonged delay in consular processing a marriage based as opposed to a K1 visa. Limit the delay; most will suggest that you remain on track with the K1 visa. A U.S. citizen has much more control with a K1 visa, where a foreigner is possibly marrying just to get a green card. You both have 90 days to live together, or nearby, then make a decision as to whether to get married with a K1 visa admission. It will be easier to see whether your foreign spouse has genuine interest, where they are in the U.S. spending time with you.

The pressure of needing to depart to see your foreign spouse and the possible loss of employment due to the emotional demands upon you may require a joint sponsor for adjustment purposes after arrival, or require someone else to complete form I-134 for consular processing on a K1 visa on behalf of your fiance.

The above is general information, not legal advice, and does not create an attorney client relationship. A paid appointment or consultation is usually the best way to work out some of these concerns.