Measuring distance between certain relations in QGIS

Not sure I understand you but if you have the table you show you could try using pyqgis to calculate distance:

layer = iface.activeLayer() #Click layer/table in tree. I have a excel table

#https://gis.stackexchange.com/questions/266360/pyqgis-when-we-search-based-on-the-distance-between-two-points-is-the-measurem
distance = QgsDistanceArea()
distance.setEllipsoid('WGS84')

fieldnames = [f.name() for f in layer.fields() if f.name().startswith(('fr','to'))] #List fields starting with fr and to
field_to_update = 'distance' #Change to match the field you want to store distances in

with edit(layer):
    for f in layer.getFeatures():
        p1 = QgsPointXY(f[fieldnames[0]]/100000,f[fieldnames[1]]/100000)
        p2 = QgsPointXY(f[fieldnames[2]]/100000,f[fieldnames[3]]/100000)
        m = distance.measureLine(p1, p2)
        f.setAttribute(f.fieldNameIndex(field_to_update),m)
        layer.updateFeature(f)

Thank you very much for your support.

I managed to do it.

Use the plugin "PointConnector" to create lines between the busstops. Then just use the "add Geometricattribute" tool.

Easy but very effetive.

Tipp 1: Only use WGS 84 Tipp 2: Be careful while creating the from-to-list for PointConnector. Excel rounds the zeros , therefor 10 is converted to 1. Tipp 3: PointConnector: Read the Python concole if errors accur. It helps alot to understand what went wrong. Sometimes just a new project with the same steps solves the problem. Or you can use the "repair geometrie" tool

Hope this helps.