Nesrine, don't worry about using us as therapists. That's what the forum is for.
I am worried about your post at the top of the page for two reasons.
Firstly you are talking about getting emotional filling in application forms and secondly you are talking about wanting to prove yourself to those who doubt you.

Firstly, you don't need to be proving yourself to anyone. Nobody who doubted you is going to care one jot about whether you succeed or not and these people don't and shouldn't matter to you anyway.
Secondly, we are not defined by our jobs. Please be careful about putting an academic job on a pedestal. An academic job is an almost exclusively administrative job. If you want to teach, do research or become an administrator, there are millions of jobs out there which are considerably easier to get access to and with better pay and conditions.

I spoke to my old supervisor a while back and asked him why so many people were putting themselves through up to 10 years of hell trying to snag a glorified admin job. His response was that most postdocs simply don't realise that the job is almost completely administrative. They think they'll get to do great research and teach the next generation when in reality they'll hire students and postdocs to do the research and if they are lucky they'll get 3 hours teaching in the classroom each week for 24 weeks of the year.

Well good luck with this but you are going to have to learn very quickly how to have disagreements with your bosses in a suitable manner. You simply cannot avoid intellectual conflicts in life without causing irrepairable damage to your career.
This is of course your PhD and you need to decide what the best approach is for your situation.

It is quite common for people to do postdocs in an area different from their PhD.
Medicine and Biology are intimately connected anyway. I imagine some biology postdocs would be needing a medical background, especially if dissection of an animal is required for example.

Ah beware the German obsession with always being "correct". There lies the path to madness lol.
None of this will help you when it comes to saying names such as K.A. Sheidt, Weiping Dong or R.A. Fuck.
I kid you not, those are real names of scientific researchers. All of them are scientists :-D
How would you handle those?
Shayt and Fook are easy ways around the outer two but the middle one is a problem. Wiping or Weeping are as bad as each other.
The German method would have you go straight for the correct pronunciations. Your audience would be braying with laughter. Good luck with that :-D

Nesrine87, I completely recognise the swings in mood and the external validation thing. For me, I overcame both when I stopped valuing the opinions of others over my own. At the time I was receiving praise for academic prizes I was winning when I knew myself that those achievements were based on weak background knowledge. I realised that I am best qualified to judge how good I am.

Having secured your PhD, I reckon you are now in the same position to judge yourself better than anyone else. You shouldn't think that this is somehow conceited or arrogant though. It's just a fact that you are now best placed to know yourself. If you can begin to believe this about yourself, you might find your self esteem is bolstered, you become more emotionally grounded, you seek less validation from people who really are no better qualified to judge you than you are yourself and you might find yourself calmer and more focussed as a result.

Your PhD doesn't need to be a single question.
It can be a series of related problems which overall form a body of work in a specific area.

For example, I started out by taking on ideas from my supervisor and then expanding them as I did the work and saw other opportunities. By the end I was making up my own ideas and implementing them.

This method is much less risky than looking for a single massive question to work on and you get lots of smaller wins along the way. It could allow you to quickly implement some very narrow and specific ideas of your su-pervisor before gradually moving on to take over yourself.

You could perhaps adopt this method.

Personally, I use my best effort to pronounce it. I don't mind being wrong and I don't mind being corrected either.
If the names are tricky, I'm sure you won't be the first to stumble over them.

By definition nobody will be an expert in all the areas covered by your research. As rewt says, it is your job to communicate with your examiners on that basis.
I am with rewt on this I'm afraid. If your examiners are not clear on the overall purpose of your research, this is absolutely on you to fix it.

I had this problem with some of my thesis as well. I simply wrote a paragraph in my response to indicate that I was clarifying points which I had made unclear in the original thesis and thanked the examiners for highlighting their concerns and that I hoped I had now resolved the issues to the satisfaction of the examiner. There were several instances of this. I didn't just blindly do what they asked but I did need to make sure I wasn't defensive in my response.

You are way too early to be worrying about this.

Is your supervisor correct when these eventual objections about your ideas are raised?
Evaluate what is causing problems in your original ideas and use this to learn how to better evaulate further ideas yourself. Eventually the idea is that you'll learn to produce ideas which won't be easy to dismiss and you'll have your solid ground.

Is he correct or not about the quality of the theoretical results?

This is a horrible experience to have gone through but there is a lesson here for anyone who finds themselves in a situation where they are relying on the results of others to base their entire PhD on.
Never ever trust anyone.
Check and re-check the raw data.
Re-run some of the experiments to be absolutely certain of the credibility of your starting data because failure to do this can be catastrophic.
At the start of my PhD I was asked to add to data run by another student. I had a quick look at it, saw a couple of spine chilling things and decided to ditch the entire lot rather than take a risk.

I'm afraid I have no idea what to advise here other than to take a bit of time off to consider starting again. On the positive side, you've been given the opportunity to start again. I would seriously consider accepting it.

How long have you been looking for a postdoc?

Remember only about 10% of fellowship applications are successful. I think that percentage is right.
I was warned by several academics when I came to the end of my PhD that who you knew was significantly more important than what you knew.

Filip96, it's my mistake here. You mentioned the Masters degree in your first post and I missed it.
As long as you are not prioritising it you will be more likely to make a good decision. So many people get obsessed with rankings and reputation over everything else and it causes no end of trouble for them.
Good luck with your studies.

FilipJ96, I am not sure where you are getting your information from as regards the correlation between university rankings and the quality of student. During my PhD I found no such correlation in my encounters with those from a wide range of unis.
Your other problem is that you may not be working in a team in the way you may imagine. Your PhD is supposed to be and probably will be largely a solo pursuit. Certainly if you want an academic research career, at some early point you are going tp have to show a large amount of ability to work independently. You seem to be suggesting that you need others around you to drive you. That isn't a healthy place to start your PhD from.