Germania,
I've never had any luck using the refresh symbol - 
Only clicking on the Home works for me. As far as F5 goes, I use my Chromebook to remote to my Windows computer that runs SF. I have a hard time remembering the Chromebook keyboard shortcut equivalent to F5. I know one of them is Control-R, but that doesn't seem to work either. Likewise, I think it used to be Search key (AKA Launcher)-fifth key on the top row, but at some point they changed it, and it doesn't work. Rather than look it up every time, I just use Home, which always works.