How do I delete lines and or trains,buses etc.

Delete vehicle: select your vehicle, send back to depot. After your vehicle has arrived you can sell it (aka delete it). If you want to sell all your vehicles from one line, you just have to open the line manager. There you click on gear wheel (at the right of each line) and choose the dollar symbol. This action sends all vehivle from one line to the nearest depot und sells it on arrival.

Delete line: You can delete a line only when there is no vehicle assigned to the line. If the line is free of vehicles, you select the gear wheel in the line manager for your line und click on „x“.

All/Many fields in Transport Fever has the feature mouseover, so you can read a short description for it.

What do you mean with upgrade vehicle or line?