Sunni inheritance law

Hello. To all the honorable, respected experts please help me understand my situation and what I could possibly do. My father passed away in 2016 and he left alot of properties but didnt had a will. My dad worked really hard and earned everything while my mom help him out. My dad loved my mother alot and often he buys properties in her name. After my dad passed away, my mom took control of everything just as she had while my dad was still alive. But after 7 months, my mom got remarried and started acting very un-motherly towards us. Back then we tried but couldn't do much to stop my mom messing with what I believe is our inheritance. Now after 5 years of my dad passing, we came to know that my mom is selling our properties without our consent (we announced via newspaper in 2016 that she need our consent as well to sell or rent anything). So now when we r asking her to divide our inheritance according to sharia she is claiming that all that my dad left is hers because she finished the half done work and some are in her names. She also claims that she already had given us what we deserve which is sending me and my brother to school and marrying my sister off. My question is Can my mother claim what's actually my dad's due to the reason she give? She didnt had anything before she married my dad and my dad took care of her and a son she brought with her. Please help me out on this because I'm in such distress on the fact that my own mother would do this to us and she is threating me and my sister with our lives if we continue to seek for a rightful claim of our inheritance. May god bless you