A newbie here, please help

Hi! So I've been trying to set up an alternative to Google Photos for a couple of days now, but I'm still at square one... The idea I have is to use my Linux desktop and run a webserver is the background, so I could send files from my phone to my computer and backup pictures this way. First of all, is it even possible to have a hybrid setup like this? I was trying to configure Nextcloud. I used the AIO image for Docker, it asked me for a domain name, I used duckdns to add a DDNS to my router to get a domain. For some reason the domain I made, leads to my router's settings page. Nextcloud is complaining about port 443 being closed. I know very little about networking and I would really appreciate some help with this. Most documentation I found online hasn't been helpful ._.

Edit:

The best guide: https://m.youtube.com/watch?v=5IUKE3oA7AY&t=2667s