Trade gasoline for diesel?

Hello dear forums community, I hope you can help me with my difficult decision. Currently I drive a Golf 6 as 1.6L 102 HP gasoline, but now I have to drive at least a good 1400km every month due to my studies, mostly motorway. That’s why I was thinking about whether I would trade my golf for a diesel or not that well worth it. Furthermore, if I exchange it, what then? I hope you can help me here. L Greetings and thanks already once.