schengen – Travelling outside of Germany on a German Working Holiday visa (Australian)

A friend and I (Australians) are planning on visiting Europe in August next year.
We wish to tour West and Central Europe for 4-5 weeks (on a normal Schengen visa) before entering Germany and applying for a 12 month Working Holiday visa (http://www.australien.diplo.de/Vertretung/australien/en/Visa/Working-Holiday.html)

My question is, am I allowed to travel outside Germany again (to Schengen countries) while holding the GWH visa? If I travel 4 weeks before getting the GWH visa, meaning I will have 8 weeks remaining on the Schengen visa, can I visit surrounding countries on weekends?

Sorry if this has been asked before, I was just having trouble finding an answer.
Thanks in advance!