While configuring your new iOS device, e.g. your iPhone 11 that is not yet configured, look for the "Apps & Data" screen during the initial installation. Tap on "Transfer data from Android". You can also find more information on the Apple website. It's very easy, and you don't need any other apps or service providers that you would have to pay for.

I went to Hämpu - https://haempu.ch/
He was able to help me.
For specific apps (e.g. Whatsapp), however, you need extra transfer apps, which apparently have security gaps.