apks files are installed using Split APKs Installer
xapk files are installed using XAPK Installer (if downloaded as zip or bin, rename to xapk)
apk files are installed using any file manager
An indispensable helper
Google Files - file manager from Google. With Google Files, you can solve all your problems with one app. The program allows you to search, view, manage your files, as well as transfer and send them. In addition to the functions of a regular file manager, the application can clear memory and free the cache by deleting unused materials, programs and other files. If ES Explorer is not satisfied with the amount of ads, and CCleaner doesn't do its job - Google Files will solve all the problems.