Ross: I also think if your only problem was grammar, Chinese person would figure out what you meant. Just like you can figure out what someone means who speaks broken English.

Ross

The reason why Chinese people don't understand you may not have to do with grammar.

The #1 reason why Chinese people may not understand you is you may not be speaking in the correct tones. The #2 reason may be because verbs in English may not have the same usage in Chinese. For example, there are at least 3 different Chinese words for the English word "like."

I like pretty girls

He is like his dad

She looks like a good person.

In Chinese, each of these sentence requires a different word for the English word "like" ... so that's not grammar but vocabulary. 

Let's break down your above sentence and arrange them into simple sentences.

I have tried forming my own sentences = What you mean here is ("I with a Chinese person tried to speak Chinese.)

based on things I would say = based on my preferred conversation topics

 but Chinese speakers don't understand me because I use English grammar = but because my grammar usage is incorrect, the Chinese person didn't understand. (in Chinese, the reason is said before the result)

So after all that is said and done ... I will try to translate your above sentence based on my imperfect Chinese

我对一个中国人讲中文关于我最喜欢的话题， 但是因为我用了错误的中文语法，所以他听不懂我。

"Man, that girl is HOT, Dog! Break me off a piece of dat!" .... This made my day. Thanks Dawei Zhijiage.

Chinese and English have very similar grammars! It's part of the reason I decided to make that my L2 first (as opposed to something like Gaelic or Arabic). The only differences I have found to be difficult are discussions about time and use of prepositions. Other than that ... very similar.

Both Chinese and English are SVO languages (not the grammar majority in the world). Grammars like Japanese (SOV) are the majority. While languages like Gaelic (VSO) are among the least spoken grammars in the world! I would agree that it must be your tones.

Tones are more than likely your biggest problem, that or you may have a problem with your interlocutor (maybe they don't understand your topic or don't want to talk to you, or are shy, or maybe your conversation is judged to be inappropriate? It's hard to say without more detail.)

Oh... you can't use "and" (he) like you would in English. It does not link two sentences but only two nouns - I believe. And depending on the language... Grammar is acutally very unnecessary for human communication. For example:

A bear look behind you out.

Pregnent is daughter your.

And some languages (like Russian), word order does not matter at all. Try talking about a subject you dont prefer? 

Thats all I got,

Nick

here is a translation from a Chinese friend ...

当我和一个中国人用中文讨论我最喜欢的话题时候，由于我用错了语法，他就不明白我的意思。

the literal translation is:

When I and a Chinese person use Chinese to discuss my preferred topics, due to my using wrong grammar, he just don't understand my meaning.

how different is that grammar from English?

but even the way I wrote it at first, a chinese person would still understand what I was saying ...