Letsencrypt, Docker and reverse proxy

Hi Party people,

I am running Quickbox now since a month and I am really happy with it. After some struggle I finally got a SSL cert for my domain up and running. Everthings works good.
I wanted to use some other apps that are currently not included in Quickbox. In particular lidarr and Organizr.
So I installed docker and got those containers running as well. And here is the thing I cant figure out for now so I am looking for someone who has more experience with it:
I want to use those docker apps with my signed SSL certificate. Currently those apps are reachable through http and a port. It looks like this for now: mydomain.com:8989. the goal is to reach each container throught https like mydomain.com/lidarr or even with a subdomain like lidarr.mydomain.com
I read a bit about it and came across this article: https://www.linuxserver.io/2017/11/28/how-to-setup-a-reverse-proxy-with-letsencrypt-ssl-for-all-your-docker-apps/

However I dont wont do mess up my Quickbox setup.
Has anybody been in the same situation like me and how did you solve it?

Thanks for your feedback!