fixed some minor typos in the docu.

doc/html/_sources/setup-standard.txt

@@ -770,6 +770,11 @@ and ``C:\cygwin\bin\bash.exe`` so that they are executed with administrator priv
 Mac OS X / macOS
 ----------------
 
+.. warning::
+
+  2019-10-10: macOS 10.15 Catalina: ``macport``/``fink``/``homebrew`` and hence ``musrfit`` are not yet ready for 
+  this version of macOS. Likely to be ready by end of November 2019.
+
 .. _MacPorts: https://www.macports.org/
 .. _Fink: http://www.finkproject.org/
 
@@ -779,6 +784,12 @@ or `Fink`_ —  which provides open-source software is employed to fulfill the b
 In the following, both possibilities (using MacPorts or Fink) are described but it is emphasized here that 
 it should be followed only *one* of the possible routes . 
 
+.. warning::
+  
+  If you decide to upgrade your macOS, e.g. from ``High Sierra`` to ``Mojave``, you will typically need to 
+  unistall ``musrfit``, ``ROOT``, and `MacPorts`_ / `Fink`_ first, do the upgrade of the macOS and start the 
+  installation of `MacPorts`_ / `Fink`_ , ``ROOT``, and ``musrfit`` from scratch!
+
 .. index:: macports
 
 Requirements (MacPorts)