There are quite a few resources available for learning spoken Cantonese but i've found it difficult to find resources to learn Cantonese grammar.
For example, the sentence "he asked me to send you some photos" is, in my opinion, not a difficult sentence to translate in many languages but it seems particularly difficult in cantonese:
佢叫我 send的畫比你
keui yiu ngoh send dik waak bei nei
he + ask + I + send + of + photo + ? + you
I have found this is called the "passive voice" but i don't understand the sentence order or why/where this "bei" is used.
Does anyone have any good resources for learning cantonese grammar, especially making sentences?
I'm not a linguist so I can't really answer your question, but IMO the "的" should be "啲", which means "some". A direct translation could be "He asks me (to) send some drawings/paintings to you. "
The "bei" relevant to your original question should actually be "畀", which means "give".
To express the meaning of "comparison", the "bei" should be "比". For example, "我比你高" means "I'm taller than you". This is where your confusion comes from; the original sentence in your question does not really use the right word.
Some people tend to mix the usage of 畀/俾/比, IMO the first two can somewhat be exchangeable, while the last one can't. "俾" has a meaning of being passive, "我俾人打" means "I was assaulted by someone".
"佢叫我比 d 畫比你", "佢叫我 send d 畫比你", "佢叫我 send 啲畫比你", ""佢叫我比啲畫比你" all convey the exact same meaning. All commonly used.
But "的" isn't 100% the right word to use here. 的 is more like a mandarin equivalent of the (very cantonese) word 嘅 , which roughly takes on the role of a preposition to signal something that BELONGS to some other thing.
(i.e. basically you don't say "佢叫我 send 的 畫比你")
To break it down you can think of the sentence like this:
佢叫我 - he/she asks (asked, is asking) me to
send / 比 啲畫 - send some pictures
比你 - to you
I am a strong believer of practicing makes perfect. If you are interested, just find opportunities and speak / listen. Quickest to learn that way I am sure.
(Now if I could only have an English teacher that can do the same to help me on my English...)
I am struggling with understanding these character variations in colloquial cantonese, ie where 比 is a variation of 畀 meaning to/for), i can't find this lesson anywhere to learn about it
Written Cantonese almost always has the propensity of being informal. If you go to any local HK online discussion forum for example, "d" and "啲" are simply used interchangeably by many (for the sake of convenience). It is so commonly used people don't really think much about reading 啲 vs. "d".
If you go buy a book on the other hand, you will rarely see any appearance of 啲 (or "d" for that matter). Instead you would more often see the more "formal" Mandarin Chinese expression of "些" - as in "他叫我給你一些畫" instead of "佢叫我比 d 畫畀你".
(BTW the other comments about 畀 being the right word for "give" is absolutely right. My bad for using the wrong word that has the exact same pronunciation, 比)
(The only thing common between 比 and 畀 is the way these two words are pronounced in Cantonese. They have different meanings, and I wouldn't even say they are variations of one another.)
Do you already have a better grasp of spoken Cantonese vs. written Cantonese? Or are you only starting to learn both at the same time? Being a native speaker I really can't say for certain, but something tells me it may be easier to build some foundation on spoken Cantonese first, then at a later stage try to associate the actual characters with the spoken words that you already have a basic idea about (in terms of how the language is structured). Your progress may become faster that way...