Business Class seats are very average no flat bed position and not very comfortable if you happen to be tall. During our outward bound flight my seat (03C) malfunctioned and became immovable. I brought this to the attention of the crew and without apology was rudely informed that I should choose another vacant seat for the remainder of the flight. I found this unacceptable as there were no free seats accessible for myself and my wife to sit together. Eventually after complaining once more a member of the crew was able to correct the problem by resetting the mechanical unit under the chair. I would also add that the screen in front of my seat was also faulty cabin was dirty and the quality of the food was well below Business Class standard. On our return flight to Kigali before taking off we noticed that both our seats were malfunctioning and once again advised the flight crew. A member of the ground technical staff was called on board and together with the cabin crew attempted to repair the seats without success. At this stage we were politely asked if we would mind moving to the free seats one row behind. We complied with the request only to find that these seats (4A & 4C) were likewise not operational and were finally relocated to 4H & 4K. The crew on this flight were attentive apologetic and informed us that the problems with seats in Business Class are recurrent and assured us that a report would be filed. I personally bore the expense of upgrading our tickets to Business Class in order to enjoy a more comfortable and relaxed journey. Unfortunately this was not the case as we were troubled by the overall poor condition of the aircraft cabin and casual disregard for the comfort and safety of passengers by Brussels Airlines.