All property acquired by spouses during marriage, whether jointly or by one of them, but using the funds of both spouses or with the assistance of the other spouse, is the joint property of both spouses; in case of doubt, it is presumed that such property belongs to both in equal shares.
If you have evidence that can accurately determine your financial contribution to the purchase of the apartment, you have the right to claim a share of the apartment proportionate to your financial contribution.
If your spouse voluntarily refuses to recognize your ownership of a portion of the apartment, you have the right to petition the court to recognize the apartment as joint property of both spouses and to recognize your ownership of a portion of the apartment proportionate to your financial contribution.
If during the court hearing, doubts arise regarding the exact amount of your contribution, or your spouse provides evidence that her contribution to the purchase of the apartment was equal to yours, the court may declare the apartment to belong to both spouses in equal shares.