What's the meaning of this part?

/. {dt_String, 
     numbers__?
      NumericQ} :> {DateObject[{dt, {"Day", ".", "Month", ".", 
        "Year"}}], numbers};

You can control the time range with PlotRange. For example

data = {{{2006, 10, 1}, 10}, {{2006, 10, 15}, 12}, {{2006, 10, 30}, 
    15}, {{2006, 11, 20}, 20}};
DateListPlot[data]
DateListPlot[data, 
 PlotRange -> {{{2006, 10, 1}, {2006, 10, 30}}, All}]

Your records are made of quadruples of the form {time, v2, v3, v4}. You can plot v2, v2, v4 separately against time:

DateListPlot[cleanedData[[All, {1, 2}]]]
DateListPlot[cleanedData[[All, {1, 3}]]]
DateListPlot[cleanedData[[All, {1, 4}]]]

First you import the file into mathematica as

myData = Import["file path"]

Then you clean up the data, for example with

cleanedData = 
  myData[[1, 3 ;; -1]] /. {dt_String, 
     numbers__?
      NumericQ} :> {DateObject[{dt, {"Day", ".", "Month", ".", 
        "Year"}}], numbers};

Then you can plot with DateListPlot:

DateListPlot[cleanedData[[All, {1, 3}]]]