Stuck with pomodoro clock, help is very much appreciated!

Hey everyone,

I’m stuck with my pomodoro clock.
In short I’m having problems:
1 - getting the timer to run over and over again
2 - getting the timer label to update to session/break depending on what’s happening
3 - getting the function to stop when the button is clicked and start again from that saved time

I know my code is probably terrible but I’ve hit a wall . I’ve tried other things but nothing seems to work. I don’t want to use jQuery and I’d like to do it in vanilla JS because I need to get passed this in order to improve. But I’d appreciate some guidance because I’m pretty much stuck.

Here’s my pen:
https://codepen.io/virginiab/pen/eKoYWN

Thanks in advance!