Masks do not slow the spread and pretty much are worthless.
Most people don’t wear them correctly, and they are not designed to filter everything. Masks can filter about 5 microns, the Covid-19 is about .1 to .2 Microns, meaning it will go through a mask.
Ooh, look, someone trying to use science to establish how something works!
Yes, the virus will easily get through the mask. However, the virus doesn’t travel alone, it travels along with particles from a sneeze or a cough (or tears...) Masks worn over the face reduce the spread of those aerosols.
The mask will not prevent you from getting COVID, it is there to help prevent the spread of COVID. Safety glasses (or even normal glasses) can also reduce exposure to aerosols (the virus can spread through entry through the tissue around the eyes.)
Washing hands won’t prevent you from getting COVID, but can help you spreading it to yourself from touching contaminated surfaces and then touching ears, nose, mouth, or eyes and transferring the virus to yourself.