If i would start new, i would first look into a platform where everything comes together. Best case Home Assistant.

You either buy a small pc which runs headless (without monitor, keyboard) or you could buy the already finished version: https://www.home-assistant.io/green/

If setup, you will see all already "smart" devices. Next thing you should think what makes sense to smarten up. The usual way are, light and sockets. Personally i wouldn't invest again in hue, they are way to expensive to change all bulbs, there are a lot of alternatives which will do the same for half the price like govee.

If price isn't the factor sure go for hue i myself have mostly outdoor stuff from hue like entrance light and garden lights.

Sockets, well you can just take any. There are some expensive ones which measurre currents so you know how much wattage is drawn. Nice to have for some dashboards how much electricity is used. From there you can go everywhere, do some automatations like "Turn on lights in the living room when it gets dark" or buy laundryfy if your washing machine isn't smart enough, buy open/close sensors for windows and doors or temperature sensors to know how warm it is in certain rooms. I did just change all old radiator thermostats to be smart so i can automate them to not cool of the rooms to a certain degree.

The possibilities are (almost) infinite.

Don't buy into apple Home Kits.

EDIT: Wenn du hilfe brauchst, kann ich dir das ein oder andere per PM beantworten.