[halayli]

if you aren't challenging yourself (mentally) there is not much you can do to improve.

I recommend diving deep into problems that interest you, noodle on them until you fully understand the problem or start coming up with solutions. This also improves your intuition.

Personally, my memory (especially working memory) improves drastically after long hours and days of thinking. Memory improves as you build your cognitive knowledge map and the puzzle pieces start to connect and the picture becomes clearer.

Pick a problem that means something to you and start from there. It's sometimes hard to find such problems especially if you aren't into a particular domain. In such cases, start by understanding a domain you love and the problems will start popping.