Threema cannot be installed Sailfish 4.0.148 Koli

[Sailfish_OS_Learner]

Hello on my newly set up Sony XA2 with 4.0.148 Koli I can not install threema.apk . Clicking on it only shows open. More does not happen.

I have also read this link.

All of a sudden, install of Android-apps doesn't start any more

After some unstructured research I found that within the lxc container of Alien Dalvik there’s a directory /data/app which contains some APK data. Most of the directories can directly be mapped to an installed app. However there was a directory called vmdl2083684193.tmp with an empty file with the name of the latest apk package that failed to install. So I deleted that directory and managed to install the app and others as well. That directory is also available on the Sailfish side at /home/.an…

But I do not understand what is written there. I do not know how to access the hidden files.
Can someone give me tips.