All roads in Germany are free for cars with the exception of a few bridges and tunnels. Commercial vehicles pay tolls
'expressways' is a US-English word, so there are no roads in Germany actually called 'expressways'.
In Germany there are 'Autobahn' and 'Bundestrasse' (Federal roads). Autobahnen are for motor vehicles only, and have no traffic lights, cross roads etc. They are equivalent to the Motorways, Autoroutes, Autostrada etc. in other European countries and use the standard motorway sign used in all European countries, (click here). Road signs on Autobahns are blue.
Speed limits on Autobahn vary, some are unlimited, others are 130 Km/Hr or less. I don't know what you mean by "like other "highways"", again "highway" is not a German word and in English "highway" can mean any road.
Speed limits are shown on signs like this when you enter Germany; 50 Km/Hr in towns, 100 Km/Hr outside towns and 130 Km/Hr recommended on Autobahns, in all cases unless marked otherwise.
Bundestrasse can vary from a high speed rural dual carriageway to an urban road. Signs for Bundestrasse are coloured yellow.
Below that all there are unclassified roads (no road numbers on signs).