Self-Hosted Main

I want to run my own public supertux cart server since when i connect localy with my friends if we are more than 2 ppl any other will time out and noidea how to fix it so i thought this could be a opertunity on how to secure a exposed server.

I watched the techno tim security video where he said to isolate it on the local network then a local reverse proxy and a cloudflare one

So if i use it in a container is is restricted from the local network? if no how do i do that and do i need a seperate reverse proxy that only has acess to the one container in like a docker network and then i expose the port and make it acesseable with duck dns and then look into cloud flare

any more things i need to reseach and what ressources do you guys recomend for me