Hi @SvenAarts and welcome to the OpenEMS Community.
So many questions here… would have probably been better to open a new thread.
In general I do recommend following the Getting Started Guide (Getting Started :: Open Energy Management System). Once that works including Edge and UI, you can start replacing the simulated components with real ones.
In your case it sounds like you are deploying Edge and UI to a separate computer (e.g. a Raspberry Pi). Be aware that in this case you should build the UI with ng build -c "openems,openems-edge-prod,prod", adjusting the environment file if required (https://github.com/OpenEMS/openems/blob/develop/ui/src/themes/openems/environments/edge-prod.ts).
You will also have to configure a webserver like NGINX and configure it for Angular applications. See → UI am Raspberry konfigurieren
Regards,
Stefan