Starting website to advocate for opensourcing research. Which language to choose

I've been a lifelong scientist, but would like to work on this as cheaply as possible. I already own a domain, but the last website I designed was in 1995 (was featured in the now defunct magazine Internet World). I don't really like the way Wordpress' themes look. I would like to design this myself, but I've been out of the loop for a while. Any suggestions, or free/cheap courses I could take to learn the programming languages necessary to make a relatively simple website from scratch? FYI, my domain is run by Google Domains (I received an invite) and I'm not sure how this effects your answers. Thank you.