After Ivanov s death, a will remained

After Ivanov’s death, a testament remained, in which he bequeathed to his youngest son Oleg a bank deposit of 300 thousand rubles. In the will, he laid the obligation to fulfill a testament refusal on his sons Oleg and Alexei in favor of his mistress Smirnova E. He obliged them to buy her the first apartment for 800 thousand rubles.
After Ivanov’s death, a 2-room apartment, worth 1 million rubles, and a car worth 200 thousand rubles remained. Question: how will property be shared between brothers and to what extent should everyone fulfill a testament refusal?