Is it permissible to take out a loan with interest to cover marriage expenses if difficult economic circumstances (due to working in tourism and the repercussions of Corona) might lead to the engagement being broken off?

If you mean borrowing with interest (riba) to complete the marriage, then riba is one of the major sins that is not permitted except in cases of necessity. There is no necessity in what you have mentioned. Necessity is defined as a situation of extreme danger or severe hardship that befalls a person, such that they fear harm to life, limb, honor, intellect, or property. You can look for a permissible way to obtain money, such as dealing with Islamic banks.