Ionic 4 - App looks different on real device

I’m struggling with the styling of my Ionic app. I’m running iOS and Android simulators and styled the app accordingly. When I’m using the DevApp or deploy the app to a real device (only tested on my HTC U11 for now), the app looks completely different.

Here’s a screenshot of the Android emulator (and how I want the images to look):

And here’s a screenshot of the app running on my real device:

A similar problem occurs when I try to set a height of let’s say a card, to take 50vh of the device. Everything looks good on the emulator(s), but not on the real device.

Can anyone give me some hints how to get the app looking as I expect it to be on actual devices?

Thanks in advance