Can't acces nextcloud outside network... (truenas core)

Hello nextcloud users

a couple of days ago I made a server for my company but I can’t get it to work outside the local network…
hope somebody could help me.

information about the system.
i run a dell r710 with truenas core on it version: 10,0 u2.1
the local IP off the server is
nextcloud IP:
router: LTE CPE B2368-66 (huawei)

at first, I got the message untrusted domain i fixed the issue by changing the config.php.
here i added the IP so i solved that issue. now I can log in to the nextcloud.

after that, i tried to port forward my router on port 8282 (because that was standing next to the IP)

I tried to check the port but I don’t know where to find the public IP…
so I can’t check it… I tried to check it with my local IP but it said it was not open…

after that i went to the web and searched for the fix there i came across the fact i could port forward the port 443 and 80. I also did this. treid to check if the port was open still no confirm the port was open… i don’t know what to do now…

after some quick search on the internet i found out about using a ddns server so I made a free ddns with a public IP. I did this on the site: /
after I made the ddns I add it to my trusted domains but it still didn’t work…

do you have any explanation for this problem and better do you know how to solve it?