Internships at Lufthansa are generally only offered as full-time internships.
A second internship within the same company of the Lufthansa Group is only possible if at least one of these two internships is a mandatory internship as defined in the examination/study regulations.
In any case, a valid reliability check according to §7 of the German Aviation Security Act is indispensable for the start of the internship. You will be asked to do this during the application process. The granting of this so-called "ZUP" usually takes 4 - 6 weeks.
If a work and residence permit is required for the country of assignment, it must be available at the latest at the beginning of the internship - otherwise the internship cannot be started and carried out.