The woman below me and my husband purchased the exact same device you pictured to torture us with. It seems she snapped during lockdown as it was much more quiet than usual in our building with no traffic going by - it was a very, very busy thoroughfare in a big city heading to the freeway, but during lockdown suddenly it was completely silent outside and ...
I know there was someone who had a few blog posts about a similar issue and ultimately settled on low-cost anti-vibration pads.
Myself, I was theorizing if one could float a bed frame on a thin layer of water or air (like an air table game). Maybe not practical though.
It depends what you think should be the frequency of the external force, which will cause it to vibration. If the frequency of the external force is overlapping with any of the natural frequencies, then the structure resonates and you have high amplitude of vibration, which can catastrophically damage the structure.
Assuming that the model is adequate and appropriate, then to answer your second question:
Which frequency out of those five is right?
All of those modes and frequencies are possible in the structure. Usually the frequencies are provided in increasing order (i.e. the numerical smallest is presented first etc).
The frequency that is usually more important, ...