Kortrijk is a really safe city. I was born there and never felt unsafe. It is not that big and so you can do everything by bike without feeling unsafe. At night I already cycled home alone a lot and it didn´t feel unsafe.

It is okay, but do look out for some streets. Try not to walk alone at night. Always walk at a good pace, call someone. But in daylight Kortrijk is nice, there is not much to do. But it is safe, there are a lot of people.