Good languages to start are Python and Java. Whatever you do isn’t really important actually. In university they’ll teach you the theoretical stuff, which is hard and boring to learn on your own. For now, try to do get some basic practical experience. Look into some topics that interest you like websites, hacking (we all go through that fase), games, AI, IoT, …
You’ll get the most benefit out of the attitude you’ll acquire: finding your resources, debugging, Git, …