Andrei,
Flashbacks are memories that seem so real like we are experiencing the abuse again. Flashbacks are nothing more than our brains trying to make sense of what was done to us, I know they are very scary and seem so real, but they are only memories. THey can be triggered by seeing or smelling or feeling something you experienced during the abuse, for example, if one time you were abused you smelled a certain kind of soap, if you smell that soap again it can cause a flashback, but from my experience nothing is more of a trigger than being near someone who has abused us. They are frightening, they seem real, but they are only memories that can't really hurt us now.
Nightmares are like flashbacks, but just thinking of something of the abuse before you g to bed can trigger it, whatever is in your mind, conciously or unconciously, is what we dream about, so if the abuse is on your mind it can cause the nightmares. Nightares are another way our brains try to make sense of the terrible things that were done to us that no person should experience.
You are strong Andrei, I have seen it in you, and you can make it through, I know it may not feel like it, but you can make it through. Just remember the abuse is not happening anymore it is over. I am sorry you must still see the people who abused you, and I wish I had some advice to give yoyu about it, but the only thing I can think to say is the abuse is over, they have hurt you, and won't hurt you again if you don't let yourself be alone near them. I know it can all be scary, but you can make it through and feel real again.
scott