Issues with BusyBox on my HTC One (M8)

Hey Community!
At first I'm sorry for my bad English and if I'm wrong here. I'm German
Hopefully you understand what you read here.

My system:
Phone: HTC One (M8) (root)
OS: Android 5.0.1
BusyBox Installer (Pro): latest version (28/1.23.2)
ROM: Stock-ROM

Several days ago I rooted my phone. To use some root-apps I've downloaded BusyBox -Installer. But as soon as I try to install it, I get an error message: "It looks like the installation of BusyBox was not successful. Try installing to a different location, that may resolve the issue."
After I tried it a second time my phone crashed and rebooted.
So I chose another path. But it still doesn't work.
So I searched the web for possible solutions.
One of them was that I should install a fix via recovery-mode.
Another was that I should mount the installation path "/system".
But nothing helps.
Then I got the tip that I should install busybox on the recovery-mode. But I cannot find a .zip file.

I do not know what to do now.
I hope someone can help me.

PS: My Samsung Galaxy TabPro 12.2 (Android 4.4.2) is also rooted but there I could busybox install without issues.