I am in a 3 years PhD programm and have half a year of funding left. I realized that during this time I have to write several articles (3 months), thesis (2 months) and 1 month for preparation for the thesis defence. I am scared that I will not make it in time, and never be able to finish my PhD. Has anybody have similar experience or any ideas? Thanks a lot.

Is there a particular reason you have to be completely finished by the time your funding runs out? Most people don't and complete their thesis in the next 6 months.
The thesis is most important. Write that, then the articles. By this time, you will know the work inside out and be completely prepared for your viva.

As postdoc said, most people don't complete (i.e. submit thesis, viva and pass) within 3 years. Perhaps you can get a part-time job so you have some income while you are writing up? As for preparing for your thesis defence, there is usually a good few weeks between thesis submission and viva (12 in my case) when you can re-read papers and prepare for any awkward questions.