The solution for this problem is quite unusual but it makes sense. I don't know if it's possible for those who have windows on their computer because I did it with a macbook. It isn't possible if you already deleted the photo lock vault calc+ app. It is still possible when it is like As85 showed us in the comments.
So for those who have a mac. Make a copy of your phone on iTunes. This copy is now available somewhere on your computer. But you can't read or open it. Next step: you download iBackup viewer. You open this app on your computer.
Now you can open your copy in this app. You click on the App Store sign. You go to the photo lock vault calc+ app.
Now you see all the items which are stored in the app. You select those items. In the right corner above you see 'export'. You export all the selected items. They will be available on your computer in a file you have selected.
In this file normally their will be a file named 'com.agilitech.spycalcfree' > 'documents' > most of the items will be available under pictures and movies, but also under 'PVassets'.
Thank me later ;)
