First of all, I recommend a best Cantonese learning website on the Internet/
Listen more and speak more, and master the corresponding laws between Cantonese and Mandarin.
First, listen more: the bookstore has Cantonese learning materials and CDs (or tapes). Buy a set to listen to every day. When visiting a market or shop, pay attention to the conversations of people around you, try to understand them, and always create a language environment for yourself.
Second, speak more: Just like learning a foreign language, learn three sentences every day from the beginning of daily conversation (not much, that is, learn three new sentences every day, review three sentences the day before yesterday and then learn new words), and use them after learning, not afraid to laugh, because others' laughter is a kind smile. At this time, you just need to ask others what they said wrong and correct it immediately.
Third, master the corresponding laws of Cantonese and Mandarin: Cantonese and Mandarin are both Chinese, and their initials, finals and tones have certain corresponding laws. Mastering the corresponding laws between them will get twice the result with half the effort. Generally speaking, Cantonese has more sounds, rhymes and tones than Mandarin. That is to say, a word with the same initial in Mandarin may be divided into two or three initials in Cantonese, such as the initial k in Mandarin and the initial k, f and h in Cantonese. For example, the initial k stands for "loss", the initial f stands for "bitter and broad" and the initial f stands for. So do vowels and tones. There are nine tones in Cantonese. Pay attention to which two tones in Mandarin are equal.
In a word, language is a skill, and you can't learn it just by understanding. You should listen and speak more, especially more.
I wish you learn Cantonese well as soon as possible! However, Cantonese is not spoken the most in Shenzhen, because Shenzhen is an immigrant city, and Mandarin is commonly used, while Guangzhou Foshan speaks Cantonese.