NSOperationQueue blocks UITableView

The following code is by another employee at my company, but i have to solve the performance-issue now...

The method 'deleteObjectAndAllDependencies' deletes the project and the related data from our SQLite DB...

The tableView isn't usable still everything is performed. How can i speed up this process? Without using functionality.

-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {

if (editingStyle == UITableViewCellEditingStyleDelete) {

    if ([[SARAM RAM] selectedProjektIndex] == indexPath.row) [[SARAM RAM] setSelectedProjektIndex:0];

    NSBlockOperation *start = [NSBlockOperation blockOperationWithBlock:^{

        [[SAAufmassProject popFromDatabaseForGUID:[SARAM projektPool][indexPath.row]] deleteObjectAndAllDependencies];

        [[self projectData] removeObjectAtIndex:indexPath.row];
    }];

    NSBlockOperation *refresh = [NSBlockOperation blockOperationWithBlock:^{

        [tableView beginUpdates];

        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];

        [tableView endUpdates];

        [self dataHasBeenDeleted];
    }];

    [refresh addDependency:start];

    [[NSOperationQueue currentQueue] addOperation:start];
    [[NSOperationQueue currentQueue] addOperation:refresh];
}

}