"built to contain heat". sigh. I'm not going into a thermodynamics discussion. Seems like europeans can't grasp the concept that insulation works both ways.
Anyways, get an AC for the living room and use a fan to push the cool air into your bedroom at night. Yes, it's not ideal. But sleeping on 40C is worse.
And also something something "60 kg AC". yeah, you're doing it wrong. I just checked and my 7000W Daikin is less than 30kg for the heavy part (the outdoor unit).
As for the install, I got tired of idiots here doing terrible jobs. I just bought all of the tools and nowadays I install and service my own air conditioners and have zero regrets. And no, you don't need any license to do this: the refrigerant is inside the outdoor unit from the factory, so at least for the initial install (and for the next 10 years if you do it right) you will not need any refrigerant.