@robveldmanfotografie Hey, that’s a cool photo! Speaking of scanning quality it is really hard to tell what’s wrong as there are too many variables involved like exposure, development and exposure during scanning. I recently made a development mistake and under-cooked my film, producing lower-contrast negatives. NLP really struggled with those!
I will say though that @Digitizer is right: you should not have so much light blazing right into the lens. Ideally you want everything blocked out, i.e. the backlit negative must be surrounded by absolute blackness. I can’t say this is the reason your results are disappointing, but it is a well-known anti-pattern.