Hi all!
Just wanted to let anyone who ends up in situation as myself that I managed to get it working. Finally! 
If I can, anyone can.
So there is something called CG NAT. Basically, whichever Dynamic DNS service you try to use and you copy paste your public IP address it doesn’t work. Why? Because it is not you behind that address, but a group of routers from your ISP. I called my ISP and said I need them to get me out of CG NAT and that resolved part of the problem.
Now I could connect from inside LAN on port 5000 (for what reason this affects LAN I really don’t know), and from outside but only on port 80.
Then using ChatGPT I troubleshooted the problem, and it turns out that the container “nginx-proxy-acme” which is responsible for LetsEncrypt certificate option could not resolve any web addresses like it didn’t have the right DNS nameservers. This was resolved with updating the /etc/resolv.conf within the container, but that option is not persistent (it stops working after the container restarts).
ChatGPT proposed to remove the container and recreate it with some options but I wasn’t sure if there are some volume binds or some other thing important so I searched for some other option. Then ChatCPT proposed to update /etc/docker/daemon.json with dns nameserver addresses but this file was non existent in my system and I guess was not used and this option did not work.
So I tried something else: In Portainer in nginx-proxy-acme container option I added this container to “bridge” network and magically the problem was solved 
I don’t know if someone should update the docker-compose.yml file in the network section for this container so other noobs like me don’t at least have this problem
Thank you and have fun!