Is Hakka just Minnan?

no, it's quite different. Minnan dialect is generally spoken in some places in Fujian and Taiwan Province. Meizhou City, Guangdong Province, is an authentic Hakka "world Hakka capital".

However, there are many Hakkas in Taiwan Province (mostly moved from Jiaoling County, Meizhou), so there may be some similarities between Hakka dialect and Minnan dialect. Some Hakka dialects are like Mandarin, and some are like Cantonese (that is, Hong Kong dialect). I can teach you a few words of Hakka.

Because I am an authentic Hakka, I come from Meixian, Meizhou.

such as: get (me), press (you), Laotai (younger brother), Aji (elder sister),

Aba (father), Auntie (mother), Auntie (aunt), Ah Q (uncle), Bye-bye, etc.