Where should I take my iPhone?

I have taken my iPhone 4 to numerous labs and each one of them ruined it a little bit more. While in the beginning I just didn't have RIL (Phone, SMS, 3G) working now the back camera, Wi-Fi and bluetooth aren't working either. Additionally the home button is a bit stuck. I opened it up and I saw I'm missing some part. This part which sits on the battery connection to the logic board https://iphonerepairmiamibeach.com/store/iphone-4-gsm/battery-fasting-piece is not there while all the other connectors are connected appropriately. I was wondering if that piece or (https://iphonerepairmiamibeach.com/store/iphone/heat-dissipation-mother-board) this which is also missing can possibly cause these issues. And also another question is how do I send my iPhone to Apple for repair because they are the only ones I can trust anymore with it, where can I find more information about this?

Added (1). I would like to mention that I don't have a retail Apple store in my country (Israel) and I would want to know about shipping it overseas, shipping prices and the possibility of it. And if I even should try that instead of just buying another phone because of the price.

You have to go to an apple store. I had an experience like that once & I brought my phone to a different little iPhone fixing stand & they screwed up my phone. In the end I had to go to apple anyways to buy an entire new phone, so just save yourself the trouble & go into apple. They'll set you up an appointment & then you'll be in as soon as possible & they'll do whatever they can.