First of all, I'm an absolute beginner and have almost no idea about photography and cameras. If I misunderstood anything, please correct me.
The reason why you don't look like yourself on selfies is the wrong setting of the focal length, which is usually around 32mm on the front camera. A focal length of 50mm comes closer to the human eye and ensures a true-to-life image. I think I can remember that you need about 1.2m distance to the camera.
My question now is how and where can I set the focal length on my Huawei P30 Pro accordingly in order to achieve such a result. If you know videos that explain such basics well, I would be very grateful.
You can't set this on your mobile phone. You have three prime lenses and the software "simulates" a zoom…
You can't set this on the front camera, as it does not offer a zoom.
You can stand no more than 1-2 meters away and then crop the picture later so that you can be seen larger.
Use the rear camera and zoom 2x into the picture, that is exactly 55mm. The best thing to do is to get a small mobile phone tripod for such photos and then simply set the self-timer.