Not sure what part of the video the German word is referring to, so no idea how to translate.
Overall I think things look very nice. The biggest suggestion I would have is that when you are heeling, to move out faster with longer strides. Her movement is very stilted and unnatural because of the slow pace and stretching up for the lure. When working with a lure like that for heeling, the dog isn't learning position so much as they are learning muscle memory for the mechanics of heeling, so you want to practice the correct mechanics so that is what her body becomes conditioned to. Fine tuning position in slow motion is fine, but for that the lure needs to be removed as when the lure is there the dog isn't really thinking about position, but just following the lure wherever it goes. Here I would use a spotter to help you dial in what is for her the best pace at which to move so that she can stride freely and enthusiastically, without lifting so much in front that her rear is crouching too low, stutter stepping or other ways dogs often have an unnatural gait in heeling.
So depending on what you're goal is for any given session, I'd change those things. Move faster and stride out when using luring to build muscle memory mechanics, and remove the lure so she has to really pay attention to where you are and her orientation to you, not just follow the food, if fine tuning position.
If your reference to using a mirror or spotter instead of looking down is with regard to heel position, there are downsides to both. A mirror is obviously an unnatural prop that you have to figure out how to hold, and the problem with a spotter is that by the time they have communicated to you that something is good and needing reinforcement, or bad and needing fixing, usually the moment has passed.
It's best to learn to keep your upper body square, but look at the dog down out of the corner of your eye. Or if that isn't possible due to certain female frontal appendages getting in the way (a problem I also have), then rather than dip your shoulder and head down to look, bend slightly at the waist. This way you can keep your upper body square, and present a square sight picture to the dog, just a slightly lowered one. The problem with dipping the shoulder and head to look down is that the dog becomes accustomed to that sight picture. And then when the handler straightens up and faces forward, suddenly the dog is crowding and crooked because the dog is trying to obtain the same sight picture that they are used to and think is correct. Bending at the waist allows you to remain straight in relation to the dog, not crooked so there is less chance of the dog getting crooked when you straighten up to maintain the same orientation to the handler that she thinks she's supposed to have.