Aim for 320kbps MP3s for the best audio quality, though lofi’s "fuzzy" nature makes it more forgiving on lower bitrates.
Many independent lofi producers upload tracks and enable "Free Download" buttons in exchange for a follow or a like.
The downtempo beats (usually 70–90 BPM) help lower your heart rate and keep you calm. How to Find and Download Lofi MP3s
The gold standard of lofi. You can find their official "Study Girl" mixes on their website or Bandcamp, where many artists offer "name your price" downloads.
Most tracks are instrumental, meaning there are no lyrics to distract your brain's language processing center.