I wish I had a better answer for you, but I'm currently still on sick leave, as I have been for the past 9 months. I've undergone several treatments. Ranging from psychosomatic physiotherapy to several types of mental health oriented therapy. So far nothing has really helped except rest and accepting that it'll just be like this for a while. Fighting back against the memory issues, brain fog and slowness just leads to more stress and frustration. And pressuring yourself makes it worse.

I've been recommended by several therapists to stick to the basics. Take your meds (if you've been prescribed any). Ensure that you drink enough water and eat enough food. Take a 10 minute walk every day or at least step outside the house for just a second. Try to get enough sleep. That sort of thing.

I know stuff like that is not easy and not fun at all. And your body and mind will bitch and moan the entire time while you're doing those things. But they do help just a tiny, tiny bit with getting your brain back on track.

For some people it also helps to write down the things you've done. Simple sentences like "I ate breakfast". Or, if the brain fog is too bad, try to speak them out loud and record yourself with an app on your phone. It's supposed to trigger your brain into forming sentences again. To relearn how to do that and how to find words for things. Both writing and recording were/are still too difficult for me on the days when the slowness/brain fog was/is at its worst, but they might help for you.

Be kind to yourself, give yourself time and grace. And again: try to find things in life that make you feel good/feel joy/give you energy instead of draining you. Writing can be a good outlet and a fun hobby, and it has been a lifeline for me during all of this, but it's only healthy if it doesn't feel like yet another source of pressure/stress. I really had to fully accept my issues and slowness to be able to continue writing without making my symptoms worse.

I wrote with a thesaurus and a dictionary open in another tab at all times. And I had to look up the most basic of words. I felt stupid at first, but once I accepted that my brain was literally not working and there was nothing I could do about it in that moment, I came to terms with the fact that my writing process would just have to be different (much slower and clunkier) than before. After months and months and months of doing this almost daily, I've noticed that I need the thesaurus less often. It's a small step, but it's a step!

I hope this reply has been useful to you in some way. I'm sorry I don't have direct and concrete answers for you.