Can't delete pictures?

I have a Huawei p9 Lite and I have not been able to delete any pictures for a while.

When I delete a picture it comes in the folder where you can delete the pictures and then I delete them.

When I turn my phone back on, they're back.

Did you maybe activate an automatic backup / backup? If the images are stored and synced elsewhere, then you need to remove the images from the source.