I just want to add my good wishes too.
I had Covid mildly in July (I was only tested as the Zoe people thought my symptoms could be Covid and offered me a test. I was amazed to prove positive as I had 'only' a rotten headache, sore throat, slight rash on tummy and lethargy; I just needed to sleep 23 hours of the day) and the brain fog following on from the lethargy was quite something.
All I say is this will pass and not to rush to be better. I was helped by the fact that ironically because of Covid, I rarely needed to have a deadline for anything so could slowly recover, which you will, at my own pace.
Take every day one at a time, don't plan anything, else you may be disappointed if you are not up to participating and treat yourself gently. I would suggest upping your intake of fruit and vegetables to ensure your body has the best intake of vitamins but other than that, there is not much that you can do.
This will pass but there are no textbooks so no-on can try to predict the duration of your recovery. One day at a time, you will recover.
PS
We fight Morrison's ordering system - I can't comment on the online systems of other supermarkets but my goodness, this one is not user friendly! You not completing your order was probably not brain fog but their daft check out process!
Hope you do feel better soon