Recently, I completely stopped the "lessons" exercise and switched to "words" and "callsigns". I close my eyes, concentrate to the utmost and try to decode the words and write them down after. There are some successes.
I decode three-letter words almost 100% the first time. Four letter words 40% the first time 40% the second and the rest require more. But five letter words almost always require 2-4 repetitions to be recognized and memorized without writing.
It turned out to be a completely different matter than exercise"lessons". Fundamentally more difficult. It looks like in the previous months I just tightly linked sounds and certain keys on the keyboard.Until I ran into the typing speed on the keyboard. With a very weak image of the symbols themselves. Some kind of "trap".
Moreover, the meaning of the word does not arise for me. Because I have to first "read" (in my brain) and then still translate the word into my language. This also takes some time.
This is an all too commom problem morse -> key.
You can have 100% success at the exercises but not know morse.
This is why some of us advise writing down , and I advise not testing yourself all the time.
Try slowing down the morse a bit and then just repeating the letters to yourself as you get them.
It's maybe not such a good idea to be learning in english if you are not fluent, but short words will do . . .
You can only concentrate on either distinguishing the morse OR decoding.
Ideally you want the decoding to be an automatic reaction, so better to pick up the code and see if the letter pops into your mind without thinking too much - it will, but slowly at first.
How's your hearing ? Do you have good enough 'phones ?? ** If you can hear the code OK then it's only a matter of time . . . **
Concentrating too hard will be too tiring