Learn Italian: Questi problemi sono sempre meno diffusi. - These problems are less and less widespread.

While sempre usually means "always," when combined with più (more) or meno (less), it creates a progressive comparison. So, sempre meno literally means "always less," which translates naturally into English as "less and less."

Why is it Questi problemi instead of Queste problemi? Doesn't problema end in -a?

Yes, but problema is a masculine noun despite ending in -a (it comes from Greek, just like il sistema or il programma). Because it is masculine, its plural is i problemi, and the demonstrative adjective must be the masculine plural questi.

Does diffusi have to agree with problemi?

Yes! diffuso (widespread) acts as an adjective here. Since problemi is a masculine plural noun, the adjective changes its ending to match, becoming diffusi.

Could I literally translate "less and less" as meno e meno?

No, Italian doesn't repeat the word "less" with an "and" to show progression like English does. You must always use the structure sempre meno (or sempre più for "more and more").