Shower suddenly without pressure

The apartment above us has been under renovation for weeks. Since Friday, the water pressure in our shower has been so low that it takes me half an hour to rinse my hair. Yesterday, I went upstairs and promptly met the plumber, who admitted to having replaced pipes but was no help at all except for advising me to buy a new shower head (but that's not the issue, it’s the same in the sink).

In general, we want to move into our first home soon anyway, but this really limits me, having to get up 20 minutes earlier every morning just to wash my hair.

Does anyone have any advice?

I would simply unscrew the lower part of the faucet on the sink (where the water comes out). There is a screen inside. This is certainly dirty. Due to the plumber's pipe replacement, protective particles may have loosened in the pipe and are now caught in the screen.