I usually tell most people to start by learning HTML and CSS, then move into learning JavaScript. 
The reason is that JavaScript is used everywhere: frontend, backend, and even to build mobile apps. 
It has many use cases, which is why I think it’s smart to learn.
When it comes to deciding which language or technologies to learn, it all comes down to your end goals. 
If you want to get into tech professionally, here’s another tip: start by looking up dream job listings, see what skills/experience they’re looking for, and then use that to reverse-engineer what you should learn.