shortest route

Can you show us an example? Please paste the URL of the route from your browser.

where do you want to change the route: on openstreetmap.org ? can you post a link of that route (copy the URL shown in the browser when the route is displayed). We can then investigate why that router thinks there is no shorter route

https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=53.8659%2C27.6207%3B53.8853%2C27.5420#map=14/53.8723/27.6189&layers=N

I want to change the route: on openstreetmap.org

I expect that you would want a route that goes like https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=53.8763%2C27.5956%3B53.8853%2C27.5420 However, this https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=53.8754%2C27.5974%3B53.8853%2C27.5420 shows that the distance is approx. the same Or is there another, shorter route that I miss

but this https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=53.8665%2C27.6208%3B53.8766%2C27.6054 is already 2.8, the same as the second one you give. So the original route is shorter. while this is shorter https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=53.8659%2C27.6207%3B53.8769%2C27.5983, a little bit further, its time is the same as the original route.

The differences are really small, and the time to travel is probably more impacted by the traffic signals or junctions you have to cross than by the actual distance you have to travel.

BTW, Graphhopper (Car) is using the route you suggest and while it is 400m shorter, it takes 3 minutes longer. (play with the drop down with "OSRM" on it). So it's more in the algorithms than in the OSM data.