Thank you all for the advice. The part I am worried about is the assurance and ID. I can provide a copy of my passport, but what do they mean with assurance?
@Astrid: so an invitation letter is something i write myself and send to my friends, right? There is no formal invitation letter template?
@Liam: Even though my friends probably won’t be asked for the documents they are first timers at leaving the safe haven of EU and venture into another continent, so having all the required documents will set them at ease. Just to be on the safe side
@Charlie: Standing in front of security control with a return flight that hasn’t really been booked must have been a little bit exciting I can imagine haha.