Earlier quoted context omitted.
From my experience appliances tolerate a wide range of voltages. The outlets in my house routinely deviate from the standard 230V, with the lowest I have seen at 170V and highest at about 260V. I have not had any appliance malfunction. Edit: I am not advising anyone to deliberately do stupid things, simply mentioning that from my experience the builtin margin is fairly large.
You (or your landlord) should probably hire an electrician to get that checked out – especially the higher voltage might be indicative of some scarier failure modes. A voltage drop of 25% could also mean you have semi-broken wiring somewhere, which can cause fires or shock hazards on faulty appliances.
My first guess would be something like a broken neutral wire, making the neutral voltage depend on the imbalance of the load between the AC phases. From the little I understand about it, you could have up to the phase to phase voltage between the broken neutral and one of the phases, with the voltage dynamically changing as devices are turned on or off. It's very confusing (since everything expects the neutral to be referenced to the earth, which is constant 0V by definition), and can burn up devices.