is there a possibility to get a https certificate while only using the internal IP?
I can establish the htttps connection but chrome and other browsers always give me the “unsecure connection” warning before I can enter the page.
Is there a way to fix this?
For an internal IP/hostname you need to create a self signed certificate. If you have a self signed certificate, you need to add that certificate as a trusted certificate to your browser. The instructions for how to do that differs from one browser to the next. Search for a tutorial on “how to get [browser name] to trust self signed certificate”.
I have posted a little tutorial on my website that explains how you can create your own CA and trust self-signed certificates (currently only in German): https://mherbst.de/de/articles-internet/erstellungeigenersslzertifikate/