PSA FOR ALL DUTCHIES:
Action has this window insect screen for like 1€ and it's easy to install and works great! (at least on my window!)
If you get it now for your bedroom you'll profit the whole summer!
https://www.action.com/nl-nl/p/2505022/horrengaas/
I found using a pencil to mark ~1cm away from the corners of the window and then taping the velcro between the marks to work the easiest, then just hang the mesh and roughly cut to size: you can fold over the messy edges and then it looks clean!