Now I would like to initialize the map again and remove all the previously created markers... How can I do this? It seems to be a method like DeleteMarker is missing?
What you do to delete created Markers depends on how your data is structured.
You can delete the Markers or make them not visible or only make some visible and others not visible.
Not necessarily. Make a ListOfMarkers as you create the the design time Marker (add items to list). When you no longer want the Markers displayed, iterate thru the List and delete the items from ListOfMarkers components .
Is this more efficient? I don't know.
Yep. You are dealing with OpenStreetMap tiles. Adding Markers and Features depend on OSMs server. Several seconds does seem a bit long. How many Markers are you deleting @Taifun ? I am aware of one developer who posts around 7000 Markers; if I recall, his updates (and deletes them) in a few seconds including display time. I am guessing it may take longer to update all Features then it takes to update/remove Markers.
There is no deleteMarker method; probably because the component Markers are autogenerated. You could of course work with design time Markers instead of run time Markers and delete (make invisible very easily).