I have not been into the same problem as you are having but yeah I have been into a similar one. I also used to get forgotten what I studied few days back in Ma

I have not been into the same problem as you are having but yeah I have been into a similar one. I also used to get forgotten what I studied few days back in Maths,while studying Physics and doing a derivation. So, I used to go back to the same chapter and used to skim through it. Later I made a rule that I will be revisiting whatever I have read after one week and then after 10 days and the like. I used to go to my college by bus that used to take 1.15 hrs. So I utilized that time to revisit the lessons that I studied few days back. Now I dont know how you travel but if you use public transport and gets a seat to sit then, you can also apply this method. This will keep the concept fresh in your mind and you won't be spending any extra time to do that. Nowadays, I use to read Quora while traveling to the office.