Saving data in background thread doesn't work - objective-c

Question

I am trying to save my data in CoreData in background thread, but it crash or it doesnt work, any idea where am I doing the mistake?
When I try with main thread it works correctly, I tried to google to find some information in background thread, I couldn't find some useful article about it.
any help appreciate.
Thanks
This is the objective -c code, what I tried
-(void)insertNameAndSurnameInDataBase:(NSString *)name surname:(NSString *)surname numbers:(NSArray *)numbers labels:(NSArray *)labels{
NSManagedObjectContext *backgroundMOC = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[backgroundMOC performBlock:^{
NSError *error;
NameAndSurname *nameAndSurname = [NSEntityDescription insertNewObjectForEntityForName:#"NameAndSurname" inManagedObjectContext:backgroundMOC];
NSString *nSurname = [NSString stringWithFormat:#"%# %#",name,surname];
nameAndSurname.nameSurname = nSurname;
if ([backgroundMOC save:&error]) {
}
else{
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"NameAndSurname"
inManagedObjectContext:backgroundMOC];
// predicate
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"nameSurname =[c] %#", nSurname];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:predicate];
[fetchRequest setReturnsObjectsAsFaults:NO];
NSArray *fetchedObjects = [backgroundMOC executeFetchRequest:fetchRequest error:&error];
if([fetchedObjects count] > 0){
[numbers enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop){
id obj2 = [labels objectAtIndex:idx];
obj = [obj stringByReplacingOccurrencesOfString:#" " withString:#""];
ContactNumber *phoneNumber = [NSEntityDescription insertNewObjectForEntityForName:#"ContactNumber" inManagedObjectContext:backgroundMOC];
phoneNumber.number = obj;
phoneNumber.label = obj2;
phoneNumber.nameAndSurname = fetchedObjects[0];
NSError *error;
if ([backgroundMOC save:&error]) {
}
else{
}
}];
}
}];
}