rMBP 13" Internet connection problems URGENT HELP NEEDED

Every 5-10 seconds my internet connection drops for like a second - this problem occurs on every single Wi-Fi/router.
After I delete all files under /Library/Preferences/SystemConfiguration (resetting the Wi-Fi adapter) It works for half an hour, then it starts doing this again.

Is there any solution to this?

It works normally when in BootCamp Windows 10, it just won't work in OSX.

The worst part is that me and my girl maintain most of the contact through skype and when it drops connection (even if its for a second), skype decreases the call quality and before the normal quality is established again, the connection drops and therefore the quality and Im caught in an endless loophole of impossible communication...

Thank you in advance

 

Sounds like a driver issue, any updates available for OS X?

 

@ Burekdober - Please put spoiler tags around your images so they don't take up so much screen real estate.

On that note, unfortunately, I believe the issue you are experiencing is a widespread one with OS X El Capitan. If you can downgrade to Yosemite, I would do that. If your system came with El Capitan pre-installed, then you're going to be stuck until the next major OS update. It's in beta right now, so hopefully the problem will be addressed.

OS X driver updates are baked into each major release of the operating system (10.11.1, 10.11.2, etc) and cannot be installed individually, so as I said above, the OP is going to have to wait until the next release if he cannot downgrade to Yosemite.

 

Since I am new to the Macbook scene, how do I install Yosemite (the computer originally came with Yosemite as my friend sold it to me and he bought it a couple of months ago)

 

You can either ask your friend to download the Yosemite installer from the app store (If the system came with Yosemite then it should be in their 'purchases' list) or you can obtain one from a less reputable source. The first option is by far the better choice. Download is about 6-7GB. Downside is that there's a fair chance you will have to do a fresh installation and wipe aour disk. Since OSX makes it quite easy to backup apps etc... this isn't the end of the world. Obviously, backup files and things you want to keep...

Once you have the installer, you can try double clicking it from your OSX installation and see whether it allows you to downgrade in El Capitan. If this doesn't work (Quite likely), just download 'Diskmaker X' and write the installer to USB. Open Diskmaker and it select the option for Yosemite - it should find the installer if it's on your system - then select a USB drive with at least 8GB of space. The USB will be wiped and the USB will become a bootable installer. Reboot the system with the USB drive connected and hit the 'Alt' button when you hear that annoying 'boooonnnnnnggg' noise. Keep holding it until a boot loader appears and select the USB drive. From then on it's the same procedure as any other OSX install - select the disk manager in the utilities menu and wipe the hard disk. Then go back to the installer window and install to the blank hard disc.

It's odd though, I have El Capitan and the WiFi hasn't been any trouble - perhaps I have simply been lucky.

EDIT: Try the solution below first - I forgot that the internet recovey restores the original OS and not the most recently installed version.

 

If the MacBook originally came with Yosemite, you can use Apple's built-in Internet recovery to restore it to its out-of-the-box state.

You can use WiFi during the process, but IMO, it's better to use a wired connection. You can pick up a USB 3.0 to gigabit adapter for about $20 or so, and some models even come with a hub so you won't lose the port.