Files can't open normal. Only with a zip-Filemanager.

Hello,
I have a problem. When I download a Android-App (.apk) with my Android Smartphone from my Filebase I get the Message that the File does not supported. Only when I have installed the Android zip-Filemanager I can installed the apk-file.
When I download the same File with my PC it works normal.

This problem exists only by files in a subsubcategory.

Can anyone help me?

Homepage: https://www.beteched.de

Sample: not work https://www.beteched.de/download/android/apps/office/Adobe%20Reader_10.4.1.apk (Adobe Reader apk in the category “Android-Apps-Office”)

https://www.ads-software.com/extend/plugins/wp-filebase/

Sample: work
https://www.beteched.de/download/android/apps/Flashlight_4.9.3.apk
(Tiny-Flashlight apk in the category “Android-Apps”)