We have learned some major differences in Cantonese and Mandarin pronunciation. You can also find this in Wikipedia:

However, Mandarin’s vowel system is somewhat more conservative than Cantonese’s, in that many diphthongs preserved in Mandarin have merged or been lost in Cantonese. Also, Mandarin makes a three-way distinction among alveolar, alveopalatal, and retroflex fricatives, distinctions that are not made by modern Cantonese. For example, jiang (將) and zhang (張) are two distinct syllables in Mandarin or old Cantonese, but in modern Cantonese they have the same sound, “jeung1”. The loss of distinction between the alveolar and the alveolopalatal sibilants in Cantonese occurred in the mid-19th centuries and was documented in many Cantonese dictionaries and pronunciation guides published prior to the 1950s. A Tonic Dictionary of the Chinese Language in the Canton Dialect by Williams (1856), writes: The initials “ch” and “ts” are constantly confounded, and some persons are absolutely unable to detect the difference, more frequently calling the words under “ts” as “ch”, than contrariwise. A Pocket Dictionary of Cantonese by Cowles (1914) adds: “s” initial may be heard for “sh” initial and vice versa.

There are clear sound correspondences in, for instance, the tones. For example, a fourth-tone (low falling tone) word in Cantonese is usually second tone (rising tone) in Mandarin.

Now, let’s take a look at the grammar.
2)Grammatical Differences Between Cantonese and Mandarin:
The most noticeable one is the position of adverb 先（Cantonese Jyutping:sin1 ; Pinyin:xian1).
e.g.