can't , can not

Watashi wa nihongo o hanasenai. : I, Japanese, can't speak. : I can't speak Japanese.
(I'm not able to speak Japanese, I don't have skills to speak Japanese)

watashi : I ,
watashi wa : I (subject)
nihongo : Japanese language
hanasu : speak
(hanasa-nai, hanashi-masu, hanasu, hanasu-toki, hanase-ba, hanase)
hanasenai : can't speak

Watashi wa nihongo o hanasanai : I, Japanese, don't speak : I don't speak Japanese.
( I can speak Japanese but I don't speak Japanese)

hanasu : speak
(hanasa-nai, hanashi-masu, hanasu, hanasu-toki, hanase-ba, hanase)

Watashi wa hashirenai. : I , can't run. : I can't run.
hashiru : run
(hashira-nai, hashiri-masu, hashiru, hashiru-toki, hashire-ba, hashire)

Watashi wa hashiranai. : I , don't run : I don't run.
hashiru : run
(hashira-nai, hashiri-masu, hashiru, hashiru-toki, hashire-ba, hashire)

tobenai : can't fly
tobu: fly
(toba-nai, tobi-masu, tobu, tobu-toki , tobe-ba , tobe)

tobanai : don't fly
tobu: fly
(toba-nai, tobi-masu, tobu, tobu-toki , tobe-ba , tobe)
nomenai : can't drink
nomu : drink
(noma-nai, nomi-masu, nomu, nomu-toki , nome-ba, nome)
nomanai : don't drink
nomu : drink
(noma-nai, nomi-masu, nomu, nomu-toki , nome-ba, nome)

exception;
In Japanese, there are cases in which "noun"+"suru" makes it verb.
suru : do
(shi-nai, shi-masu, suru, suru-toki, sure-ba, shiro)
benkyou : study(noun)
benkyousuru : study(verb)
unten : driving(noun)
unten suru : drive(verb)

Watashi wa benkyou shinai : I, study, don't : I don't study.
Watashi wa benkyou dekinai : I , study, can't. : I can't study.
dekiru(verb) : can, be able to
(deki-nai, deki-masu, dekiru, dekiru-toki, dekire-ba, dekiro)