If you don't have time to concentrate and learn something new then spend that time reviewing what you've already learned.

Create flash cards (either physical or on a personal git repo you can access with your phone or computer).

https://en.wikipedia.org/wiki/Spaced_repetition

Don't put the question and answer on the same side. If using a website, require a click to see the answer.

It is temping to be constantly learning something new, but if you don't reinforce what you've already learned, then you're wasting your time on things you're going to forget.