Why it's not got power brake's and it doesn't stay running if it is not warmed up engine dies

This sounds like a case where some hands on inspection is needed. When I think of power brakes and how they are related to engine performance, I think of engine vacuum -- which supplies the "power" to the power brake booster. If you have an air leak, it can cause stalling and a loss of engine vacuum. Focus initial attention there. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops