N.V. Zaichenko died on May 10, 2005.

N.V. Zaichenko died on May 10, 2005. After her death, hereditary property remained in the form of a three-room apartment and items of ordinary home furnishings. The heir to the will made by her in life is her grandson N.A. Onisimov, who, having received a certificate of inheritance in an apartment on March 14, 2006, entered into a contract for the sale of this apartment. The household items in the form of furniture in the apartment on August 10, 2005 were taken from the apartment by the daughter of the testator A.A. Petrenko (she donated part of them gratuitously to the neighbor of the deceased).
A.A. Petrenko appealed to the court to N.A. Onisimov on establishing the fact of accepting an inheritance and recognizing the certificate of inheritance as invalid in terms of the amount of inherited property, recognizing the right to a compulsory share in the inheritance and ownership of a 2/3 share in the ownership of an apartment. She motivated the requirements by having the right to a compulsory share in the inheritance, since since 1998 she has been disabled in group III, she accepted the inheritance, bears the cost of maintaining the apartment, paying for utilities.
ON. Onisimov did not recognize the claim. He indicated that the mother had declared her rights to the apartment, disagreeing with the amount that he had to transfer to her after selling the apartment. Moreover, at the stated time, she did not apply to the notary office and did not enter the inheritance rights.
Solve the case.