that sounds like a really difficult situation and i sympathise - i don't deal with lies very well myself and find them difficult to let rest.
What I've discovered over the years is that sometimes when people feel really awful inside and can't explain what they're really feeling - because it's either too difficult to put things into words and to do so would open severe wounds that they might not be able to close up again..
Or.. because they just can't justify the way they feel without making up stories the same size as the pain they feel inside.
I still think it would be better for them to try and explain just how bad they feel without making up lies to justify/solidify the huge huge feelings that they have.. but I can kind of understand things a bit better when i look at it in this way.. what someone is really saying when they make up a disaster story or when they lie about a wife and child is that the way they feel is the way they'd feel if these things were actually true.
Either that - or they just like the attention.. but that again is a problem in itself - because when someone lies to that degree for attention.. you've clearly got someone standing in front of you and saying ''please show me that you care and please support me.. i need to be validated''
So.. to unpick things a little bit after considering things in that way;
1. Hes constantly accusing me that I did something, but I didnt. Then he gets so angry, that he doesnt want to talk with me for days. WHAT TO DO WHEN HE DOES THAT?
^^ What things has he accused you of and is there even a tiny bit of truth in what he's saying? If you take a step back from your feelings when he does this.. does any of it make sense whatsoever? ie; if you were him, how would you view things and do they make sense?
I think that when he won't talk to you for days, it's a good idea to leave him be for a while to recollect himself and come back down to reality a bit - leave him alone to regain the ability to self reflect..
psychosis in ptsd is unusual but sometimes does happen and if he's got a bit of psychosis going on, it's likely to be of the ''i think people are against me'' variety - so it is possible that he sees things one way when in the middle of large amounts of stress but then regains clarity once the ptsd has settled down.
2. Hes lying. He always talks about friends he doesnt have. Example: Yesterday he said he was with friend on grill from 2 pm to 4 pm. In that time, he was at doctors ordination. I know because I saw him from local cafe entering and leaving.
^^ I'd be tempted to let him have this one - it sounds like he's trying to make himself sound less asocial and odd than he really feels.. it's usually something that teens do but if someone knows they're a little weird or don't quite fit.. they often try and make themselves seem a bit more ''normal'' so that they feel less weird.
Second example. He told me few times that he have a wife and daughter, but they left him during the war and moved to Serbia. A week ago, hes nephew told me that he never had a wife or a daughter. Does that have something to do with the baby he saw getting killed during his time at war camp?
^^ again.. sounds like he's trying to garner sympathy for feeling lonely and he's making things up that are as big as the feeling he feels inside. It could partly have something to do with the baby he saw getting killed - when he saw the baby being killed, it probably really got to him - can't really answer that with any more than a thought though
Third example. He made up that he have a house assitant from Romania. He named her like he named the wife and daughter. When I went to his place once, he told me that she left him day earlier saying: "When you fix your life, I will come back".
^^ sounds again like he's trying to make his life sound less odd and lonely by filling his days with imaginary people to give to you.. as proof that he has people there and he's not always on his own.. so he doesn't sound too weird or anything to you..
Or.. the story could be true - unlikely from what you've said but still..
3. Most of the time Im nice to him. But sometimes I overreact when he gets angry for nothing, and I just tell him to leave. ALWAYS, few hours later, he calls me and he says that he needs me. When I meet him again, he buys me cigarettes, food, etc. So, when Im nice to him most of the time he is okay, but when I get mad hes always buying me somethin to make things okay. WHY IS HE DOIN THAT? AND WHY IS HE MAD WHEN I SAY I DONT WANT THOSE MATERIAL THINGS AND THERE IS NO NEED FOR HIM TO BUY THEM?
all i can say to this is that a gift accepted is one that honours the giver.. to accept a gift from someone is to validate their feelings and thoughts - it is an acceptance of friendship and kindness.
To refuse a gift feels like a refusal of something much more than the physical offering that is involved.
If you think of this like the way a small child offers you a mouldy leaf that they picked off the floor - they present it to you because they love it and see value in it - you are important to them so to give you the gift is a way of honouring you.. and when you accept it - you validate them.
I suggest that you treat him a bit more like a child - not in a bad way but more in an understanding of where he is emotionally at the moment. PTSD is awful and it strips you of your very identity.. it pulls apart everything you knew and were and to recover from it - you have to start by putting your identity back together again - you have to start from the very basics again.
Emotionally your friend is probably at the level of a 6 year old child and also at the level of a 95 year old man.. to have the emotions and lack of true identity that a 6 year old has child but the experience of a 95 year old is incredibly difficult to reconcile and work through.
Allow him his lies unless they are dangerous to you or others.. he will stop them as his identity builds up a bit and he starts walking in the world again.
Accept his gifts - by accepting them you are accepting him. If they make you uncomfortable then buy him gifts as well - and to the same value as the gifts he buys for you - so if he buys you cigarettes then buy him a box in return.. take them with you when you visit and give them to him.. if he buys you food then invite him round for dinner and say that you'd love to cook for him because he's your friend and it would bring you pleasure to do something nice for him because he does so much for you.
Reading up a little bit about that camp that he was imprisoned in and i'm not surprised that your friend is making up an alternative reality - he needs that or he'll fall apart.. xx