I've been using yesterday fiddler for the first time etc, and today out of a sudden I barely can open any applications installed on my computer, could It be Fiddler's fault? I also didn't have internet early in the morning but I had on other devices but I fixed that somehow.
Fiddler Everywhere is setting the system proxy (on windows that would be under Proxy Settings > Manual Proxy), and once it is stopped/closed, the system proxy should be reverted to its original state. If your Internet connection is not working after Fiddler is closed and the OS proxy settings are reverted, that would mean that the issue is elsewhere.
You could post a screenshot of your OS proxy settings (before/after Fiddler Everywhere is running) and also clarify a bit more what you mean by applications that are using *.com are not working. The HTTPS traffic won't be captured unless you have the Fiddler certificate installed and trusted but again once Fiddler is not capturing, you should b e able to use your connection without any hassle.
Note: You could post a screencast of your issue to demonstrate the case further.
I'm a windows 10 I've checked few internet options and I'm pretty sure It doesn't have its proxy.
The most likely reason not to be able to use Internet after Fiddler was used is that your OS is still using the Fiddler Everywhere proxy even after the application is closed. To confirm and resolve this issue open the Windows OS proxy settings and make sure that you are not having the Fiddler proxy (Windows Start > Proxy Settings > Manual Settings and remove the Fiddler proxy).
I seemingly cannot open applications that has Https or .com in them help pls?