I speak English well.
I play tennis badly.
I do my homework correctly.
To create adverbs we normally add -ly:
quick - quickly
slow - slowly
'good' is an adjective
'well' is an adverb
This is a good book.
I read well.
This is a good book. (NOT This is a well book.)
I read well. (NOT I read good.)
Politely - Angrily - Happily - Fastly - Quickly - Slowly - Furiously - Kindly - Loudly - Quietly - Nervously - Sleepily - ...