How can I make these kind of pictures?
(Picture 1)
I know you can just take a screenshot, but it looks different:
Even if I don't take the screenshot with iPhone 12 but instead the iPhone SE, it doesn't look like in Picture 1 (unfortunately the iPhone 10 doesn't work because it doesn't suggest for iOS 14.3).
Does anyone have an idea how I can take such a picture?
The realistic device bezel is added later via image manipulation. There is a number of services and scripts that do it.
I personally prefer using templates from Figma Community, there are quite a lot of them:
Just don't forget to check licensing – whether the template author allows you to use derived images commercially.
Disclaimer: I didn't check for that in the links I posted above, nor do I recommend any particular template.
As @ivanmoskalev said, you need to edit the image yourself (Xcode does not have this functionality built-in). You can look for mockup frames on the internet, but I prefer this app called Rotato.
It's $50 to remove the watermark. But you also get animations and lots of devices. In my opinion, completely worth it.
