Hello! I've been recently using Lightroom for Android and so for I am really content. However, when I started sorting my pictures I noticed that I somehow cannot delete the created albums/files anymore
To delete an album you need to be in the main album list view, then tap on the vertical tri-dot icon to the right of the album name that you want to delete. That opens the various options for that album, which should include the Delete option.
To delete individual image files, you need to select either All Photos or a specific album. With the thumbnails for the images that you want to delete showing on screen, tap on the vertical tri-dot icon on the top toolbar, right-hand end, and tap on "Select". That puts you into select mode where you can tap on each photo that you want to delete, when they are selected tap on the recycle bin at the top.