Is it permissible for a woman traveling for medical treatment in a European country to combine and shorten prayers, given that she does not know the duration of her stay and may occasionally go out for her personal needs?

If the intention for staying in a European country is four days or more, or for an indefinite period, then shortening the prayer (qasr) is not permissible. As for combining prayers (jama'), the 기본 rule is to perform each prayer at its designated time, as Allah Almighty says: "Indeed, prayer has been decreed upon the believers a [timed] ordinance." However, combining prayers is permissible when one is unable to perform the prayer at its [designated] time, as is the view of Imam Ahmad. One should be keen to perform the prayer at its time and not be lenient with dispensations without necessity, knowing that prayer does not require a specific place, as the Prophet, peace and blessings be upon him, said: "And the earth has been made for me a place of prostration and a means of purification."