The technician installing our washing machine said that the water pressure in the pipe to which our washing machine is connected is too high, and that it will break if we use it this way. The manual says that it should be between 100 and 1000 kPa and that if it's higher we should have a valve installed. I have contacted the apartment building management company, so it is theoretically possible that they will do something within the next six to eight weeks, but they probably won't tell me when they have. How can I tell if/that the water pressure is too high (and thus, later tell when it no longer is)?
Water pressure gauges that connect to garden hose fittings are common at home stores in the US. I assume you are from elsewhere because of the units you used for pressure, but, for instance, at Home Depot the gauges are found in the lawn sprinkler area because water pressure is an important consideration for the design of a sprinkler system.
You may have to look around at stores that sell irrigation or general plumbing supplies to find one. For an online search "water hose pressure gauge" should give plenty of results. Of course I'm also assuming that your washing machine uses the same fittings as a garden hose, so make sure you get the right connector (again, standard in the US).