dear all,
I´m a third year PhD (environmental microbiology) and I´m currently write my thesis. During my PhD time I had several problems, my first project simply died out and at the end of the first year I started a new one. In my lab there were not so many expertise so most of the analysis (e.g. proteomics) were performed by companies we payed. In the middle of my second year my supervisor left the institute. She never was able to give my advise form the scientific point of view, and when she left I had to struggle to organize all experimental and bureaucratic part.
Now I feel really down, I feel I did not learn "enough" from the methodology point of view. I spent most of my time try to figure out what to do as fast as I could.
I know that PhD means, learn how to do science, which problem consider and how to approach them, but I feel I do not have any practical competence compared with other students who worked in a more structured PhD program. I feel I´m not an expert in anything , any techniques any specific topic, and I think I will not have enough chances to find a post-doc.
A few days ago an insane idea came in my mind, to quit and look for another PhD, where hopefully I could invest my time in learning methods and techniques, to be more competitive for a post-doc afterwards.
Of course it is an hard decision and I really would like to have your opinion about that!
thank you very much for your time and your help!

Hm, it is a tough decision. However, you've already said that you are writing your thesis, right? Let me share with you my experience learning how to do research:

Initially, I thought that all that was required was a good idea. However, a few journal rejections later and I'm starting to learn that there are a ton of different things to consider: have you clearly defined your contribution to the state of the art? Do your experiments sufficiently support your claims? Are your claims the right ones to be making?

How I learned all of this was by the process of peer review. I submitted (awful!) papers to journals with the high hopes of getting them accepted. But the rejections taught me a lot. The reviewers' comments were exceptionally helpful in guiding me towards learning how to properly structure my research. My advisors helped, but it was the reviewers who were the ones teaching me how to structure things. So try to publish, get rejected, and revise, and through that process learn to do science.

I'll also tell you that I had never felt that I was an expert on my topic until early into my 3rd year. I still feel that there is so much left to learn, but I feel that my knowledge is sufficient and growing to call myself an expert. It took a LONG time to get there, and a lot of other students feel the same way. Stick to it, I say.