So you accidentally deleted the "E" default keybind for getting in and out of vehicles. alas! there is a way for getting it back.

Step One: go to your Control Panel, File Options, tab VIEW, make sure you have it on for showing Hidden Files.

Step Two: go to your (C:) drive, Users, "Your Name", AppData, Roaming, Landwirt2014Platinum, Save

Step Three: delete all the files inside that Save file. and Load the game. everything back to normal. enjoy!!