I tried three methods suggested by you, and the good news is that all three seems to be working perfectly for myself. Moving away from the building has been a great help to me. Climbing up on the lorry helped tremendously and made converging edges as they go upwards, almost straight. However I am still striving to make the camera parallel to the ground, hence I am soon going to buy a tripod. And all the three techniques seem to be working simultaneously, if I don’t follow even one of the these, building become narrower as it moves upwards.
Only I understand the joy it gives to capture the building my new office is in!
Thank you so much for your help!