Is it permissible to continue working and living in Spain after repenting from a forbidden relationship with a man to obtain documents, knowing that the work came as a result of this relationship?

You must hasten to repent from this forbidden relationship by abandoning it, regretting having done it, and resolving never to return to it. As for working in this country, if it is permissible, then remaining in it is not forbidden because of that illicit relationship, unless staying exposes you to temptation or prevents you from sincere repentance and righteousness. In that case, you must leave it and move to a place where you can preserve your religion.