Question

반말을 그렇게 잘 하지는 못해요 The long negative -지 못하- is an equivalent of 못 expressing inability to act in circumstances where the subject has no control over the situation. In this meaning -지 못하- translates as 'cannot' in English. When used with adjectives, -지 못하- expresses a strong negative meaning emphasized by the speaker's dissatisfaction with the state of affairs.-지 못하- can occur followed by tense modifiers, speech style endings, etc. The -지 part can appear followed by the -가, -는 or -를 particle controlling the emphasis.Unlike 못, -지 못하- can be used with adjectives.Long negatives like -지 않- and -지 못하- sound less direct and more formal than their short equivalents 안 and 못.The use of long negatives is an appropriate way to negate long (three and more syllables) adjectives and verbs.Negatives for some verbs and adjectives can be made only with long negative forms.

Accepted Answer

I don't know how to speak casually a lot

Front	반말을 그렇게 잘 하지는 못해요
Back	I don't know how to speak casually a lot
Notes	The long negative -지 못하- is an equivalent of 못 expressing inability to act in circumstances where the subject has no control over the situation. In this meaning -지 못하- translates as 'cannot' in English. When used with adjectives, -지 못하- expresses a strong negative meaning emphasized by the speaker's dissatisfaction with the state of affairs. -지 못하- can occur followed by tense modifiers, speech style endings, etc. The -지 part can appear followed by the -가, -는 or -를 particle controlling the emphasis. Unlike 못, -지 못하- can be used with adjectives. Long negatives like -지 않- and -지 못하- sound less direct and more formal than their short equivalents 안 and 못. The use of long negatives is an appropriate way to negate long (three and more syllables) adjectives and verbs. Negatives for some verbs and adjectives can be made only with long negative forms.

지 못하 Long Negative Meaning Adjectives 반말을 그렇게