Here is a great article that explains the difference between "stare" and "essere": http://serenaitalian.wordpress.com/2010/09/09/difference-between-stare-and-essere/ Hope I helped! :)
I'm quite confuse about what this sentence means both in Italian and in English.
sto meglio-> I feel better.
better as an adjective before a link-verb -> If you are better after an illness or injury, you have recovered from it. If you feel better, you no longer feel so ill.
better as an adverb -> In a more excellent manner; in a more suitable way.
By this website:
- to do can be a link-verb https://www.yourdictionary.com/pdf/articles/150.linkingverbs.pdf .
As how I understand, in the sentence "Are you doing better today?" better can be recover from an injury (doing->link-verb, better-> adjective) and can mean that in this day, you are just doing things better (doing->verb, better-> adverb).
So my question is, can the sentence have both meanings in English,
and in Italian, can sto meglio be understood in both meanings or just as how Collins suggested, sto meglio -> I feel better (referring to an illness)