It's a fast fix:

The basic idea is to convert your points to a WKT [Well-known text representation of geometry][1] in EXCEL and export it as CSV data into QGIS. Therefore we create a new field (column) in EXCEL and call it geometry and construct a WKT LineString as Textthat can be read in qgis csv import.

In WKT two point coordinates (x,y) a seperated by a whitespace and the next point is seperated by a comma ",".

We can use:

POINT (30 10)

LINESTRING (30 10, 10 30, 40 40)

POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))

and some other options.

So we can construct a WKT for each row with the function TEXTJOIN in EXCEL.

In EXCEL use:

    ="LINESTRING(" & TEXTJOIN(" ";TRUE;A2;B2) & "," & TEXTJOIN(" ";TRUE;C2;D2) & ")"

[![enter image description here][2]][2]

Now you have a column called geometry

**Important hint**
As you live in a country with a comma as decimal sepertaor you must convert your coordinates to a format with "." instead of ",". 

[![enter image description here][3]][3]

Save your file as CSV in EXCEL.

Now in qgis import your CSV from menu --> Layer --> Add delimated Text Layer. 
Your geometry defintion is WKT and your geometry field is the geometry field you created in EXCEL. Choose Line as geometry type and your CRS.

[![enter image description here][4]][4]

Now you have a regular line layer with your fields and attributes in qgis and you can calculate what ever you want. Perhaps you must reproject your layer to get the length in km.


  [1]: https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry
  [2]: https://i.sstatic.net/6dZ4P.png
  [3]: https://i.sstatic.net/TOQKI.png
  [4]: https://i.sstatic.net/pEDA2.png