2011 theme: dropdown menus don't work on tablets.

i use the twenty eleven theme with drop down menu and want my site to work on tablets, too. I could not verify on iPad, but the dropdown menus do NOT work properly on samsung android tablets (although I do use the wptouch plugin).

my website: https://www.praxis-muehlbacher.at
problem: dropdown menu can be seen, but the links cannot be accessed.

i am new to wordpress (having used dinosaur software frontpage before) and apologize if my questions or problems are trivial – I could not find a user-friendly answer anywhere by just searching the net.

i would really appreciate any help or suggestions…!

thanks a lot.
i asked the question once before two weeks ago, but …. no answer!