Stuck in gta iv mission!?

i am playing grand theft auto iv and im at the mission called "ivan the not so terrible". i got to the part where you have him cornered on the roof and can either kill him or save him. i killed him and called vlad, and he said something about niko's cousin's girlfriend being really easy or something like that, then niko told him to "f off" then i accidently fell off the roof and died. when i got out of the hospital i started walking around continuing the game but i havent gotten any calls from anyone that has something to do with the main storyline for like, 4 or so in game days. is there something else im supposed to do to continue the main story? o and another quick question, i still dont have any guns at this point in the game but the rest of the forums i look up about this mission people were talking about already having guns. when do you unlock guns? and do i have to do something? sorry this is so long but i really really need help. thanks