Dynamic speed 'how to' guide

First of all, thanks for the beautiful project that is Valhalla !

I'm a complete beginner at using Valhalla, so I read the doc and found about https://gis-ops.com, which is an excellent site by the way.
I ran some test with the docker image gisops/valhalla:3.0.9, that went nicely.

Now, I have read about dynamic costing, but I can't figure out how to use it...
How dynamic is it ? Can it be real-time dynamic ? How do I change the costing ?

My need would be for example to block a road due to a flood (unpredictable), or block a road every sunday due to a market (predictable).
I would also need static costing, but distinct from the OSM data. Is that possible ?

I'm also looking at what can be done whith GraphHopper, and I found the `block_area` parameter in flexible mode, and this blog post for dynamic costing :
https://www.graphhopper.com/blog/2015/04/08/visualize-and-handle-traffic-information-with-graphhopper-in-real-time-for-cologne-germany-koln/

Are those kind of features available with Valhalla, and if so, how ?

Thanks in advance for all your help!