I have problem with my brother who 23 years old. I am 16 and when it is prayer time my brother don't understand, every month when my period comes I can't pray. I am shy to tell my brother because when come pray time he forces me to pray. He beats me until I make pray. Or I tell Mommy only she tells him leave her alone, don't bother her she's tired, etc. but sometimes my mother is not in home and when out period comes I am scared of my brother and I make Salat. Will Allah be angry for me because I am not clean? What can I do and how to tell brother, for I am shy? He don't know about girls and for this she can not pray.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is forbidden for a menstruating woman to offer prayers or to fast as the Prophet said when addressing women: "Is it not true that a woman can neither pray nor fast during her menses?" The woman replied, 'Yes'. He said: “This is the deficiency in her religion.” [Al-Bukhari and Muslim; narrated by Abu Sa’eed Al-Khudri]

Therefore, you should repent towards Allah and should avoid performing prayers during your menses.

Know that menses is destined for the daughters of Adam by Allah. So, you should not feel shame from the fact that it is not peculiar to you, but it is common for all women. Know that Allah is not ashamed of truth. Thus, if your brother orders you to offer prayer, you can inform him that you are in your monthly period.

Allah knows best.