What are my rights in receiving the money back that I put into my husband’s flat?

You have no intrinsic right to that money, unfortunately, though if you divorce him, it is a factor that the family court *may* consider (i.e. has the discretion to consider, but not the obligation) in dividing assets or property; the court could choose to give you a larger share of assets to reflect contributions you made to improve an apartment owned by your husband. (If it was rented from a third party, you would have no recourse even in a divorce, since the third party is not part of your marriage or divorce.) The reason that you don't have any intrinsic right is that unless you had a written agreement requiring repayment, by putting money into a family member's (your husband's) property when you did not have to--were not under a legal obligation to do so--you "gifted" the money to him. When you give money to or pay costs for another without them first agreeing to repay, it is a gift; and a gift, once given, may not be ungiven or recovered. Furthermore, if you were living there for all or most of the time the improvements were being made, a court could additionally analyze the situation that you were paying this amount for your own benefit--to improve your living conditions. So only in a divorce, if the family court chooses to exercise its "equitable" (essentially, fairness-based) power to come to a reasonable and appropriate distribution of assets and, in doing so, chooses to recognize and give you some credit for the payments, might you get anything for this. (Family courts have a great deal of discretion to come to fair results in their cases, even when the law does not mandate a certain outcome.)