Novice installation on Acer h340 succes still some questions

First message here.
I’m quite a novice on networking and Linux so please bear with me.
Must admit that the process went quite smooth with the help of google, this forum and the documentation.

I got everything up and running in my lan and assigning pools, shares and a samba connection or how experts call it.

So no direct trouble shooting needed but still have a few things I’m not sure how to do or make them correct:

If I want to go to the login page of the browser (chrome) It shows in the header unsafe connection with a big red line through https.
What are the possible downsides of this message?
How can I correct this.

Next step I believe has less to do with rocktor, but since it is a cloud utility knowledge can be here.
What steps need to be taken in order to access a shared folder like a music folder on a device?
I’m still a bit staring in a fog with that.