Reasonable trip time is 30 minutes. 4 miles is about the edge of that for most people on a regular bike. 7 miles is in that range on an ebike. Sure I have ridden by regular bike 12 miles before, but the trip took over an hour.
12 miles should definitely not take you more than an hour, thats definitely a leisurely average pace. A reasonable and realistic pace for a complete beginner biking for transport is around 15mph on a regular road bike in relatively flat terrain (less than 600 feet of total elevation)