This is a HEPA filter!
You don't wash it in cleanrooms, but it's OK for home use!
https://xl-elektro.de/staubsauge...

Remove the superficial dust. To prevent it from getting into the room air, put the filter in a plastic bag and gently tap it out.
Give the dust time to settle
Then carefully remove the filter from the bag.
Clean the filter under running water.
A brush and/or soap should only be used if in accordance with the manufacturer's instructions.
Allow to dry
Put it back in the hoover.

It is really IMPORTANT to be very careful with the brush! A soft brush if necessary!
Just use hot water and the spray on the shower is the best!
Otherwise these parts will break, they will felt / fibres - you should avoid this otherwise they will clog!