Hi Tiia, Is it actually quite a challenge to create responsive landing pages (emails are easy) which are mobile optomised. As Breno noted - Design Studio built landing pages are absolute positioned and by definition not responsive. It isn't impossible to make an LP responsoive however - you just need to "break" the design studio for it to work.
I stumbled upon a great website by a person called Edrward Unthank who provided a nice set of templates and approach for creating responsive landing pages which helped me and should help you to! The approach uses the (which he nicely coined) "double div" approach!