ESL learners mix those up all the time, but they are completely different phonemes in English. For this particular phonemic distinction, Mandarin will help, but Cantonese will not. The vowel in “actually” should sound between /a/ and /e/. Smile a bit when you say it. Similar to the “a” in Mandarin quan 全 or yuan 元. The vowel in “ugly” should sound between /a/ and /o/, but closer to /a/. the lips should be neutral (neither smiling nor rounded as for a kiss), and the mouth should not be too open. The tongue position is somewhere between that for /a/ and for /o/. Similar to the “e” in Mandarin děng 等. In modern RP, in Canada, and to some extent on America’s west coast, the vowel in “actually” is now more open, a bit like /a/. In that case, the vowels in “ugly” and in “dot" will also be modified somewhat, so as to create phonemic space. Note that most Canadians (and many Americans) do not distinguish "cot-caught" or "don-dawn", although Mandarin and especially Cantonese speakers can easily do so.

Hi Alfredo, Thank you for sharing! :)

ACK-SHUALLY