I've encountered a bug where I immediately jump into the vegetable farm quest without even doing the quest before that, which means that the farm don't exist which then means I can't finish the quest ... What should I do, it's stuck, I've made a lot of progress so I can't reset. 

How did you "jump" into the vegetable farm quest? Did you receive a quest from Kayelinth when you talked with her at the sleeping chambers, but you're missing the steps before that? Or what happened? 
What does your quest log say? Do you have an old quest for this quest line? Is the current step of the quest something you can do?
Do you have an auto-save in slot 19/20 to go back to before that bug appeared, if it is a bug?
Can you post your save file?