I'm guessing the witch your mentioning is Vicoria? (I translated your response so it might not be translated properly by just using the internet.)
Anyways you don't have to fight her, if you have met Arion and have a pretty good relationship with him (I prefer to get a heart with him or two before asking, haven't asked without one yet.) you can ask him to help you deal with Vicoria's lust and you can continue.
Once that is all settled you will go to the forest path, find the cave and enter it.
And if you don't have a good relationship with Airon then you can fight her using save scumming (where you make a save and reload it to better your chances if your turn didn't go well) your way through and I recommend using healing potions, lust potions, and restrain potions watching the bars associated with them.
Hope this helps.
Oh sorry. I thought I wrote it in English but it was a mistake. Thank you for your kind reply.
The witch I mentioned is a witch who lives in a swamp. I fought in the Oak War and Vicoria was sacrificed. (Maybe) I don't exist in the cave anymore. I have a good relationship with Arion, but that's all..
No need to worry about the language mistake it happens. At least now I understand more with the added context here.
So since you did the Ork war and Vicoria is gone I believe that you unfortunately can't get the farmstead option from what I know.
So if you have an earlier save from before you can go back to and free Ste (the character for the Farmstead), backtracking will suck but I don't believe that there is another way at the moment unfortunately.