Learning two language at the same time: Chinese and Japanese

I'm currently learning both . After doing some research on studying Japanese, I decided to learn both Chinese and Japanese since they used both the same character system. Maybe a lot of people don't actually know this that the Vietnamese in fact uses the alphabet character for the meaning of the words in Chinese except that the grammar is completely different. So I learn Chinese characters in Vietnamese so that I can really know the meaning between two character that have the same meaning in English. For example, 想 and 思 have the same meaning as thought but they are quite different in my language in some aspect. That's why I can learn the kanji and how to combine them because it was actually transfering my language in a different sound, but still a lot of words still don't follow like that.

Let's get to the point here. I need some help to adjust my method. I got all the material needed for Japanese but not for Chinese. The fact is that I can't find a good grammar guide for Chinese as good as Tae Kim in Japanese. I was kinda stuck when I can only speak Chinese by linking all the words I know together. So I want to find some good grammar guide for Chinese. Can anyone help me? And on this topic, if someone who also learns both Chinese and Japanese here, you can post here some thoughts you want to share with.

My learning style is completely different from a lot of people. For Chinese, I focus on vocabulary while for Japanes, I concentrate on reading, speaking and listening. I don't concentrate on both language on all four skills: reading, writing, listening and speaking. Because I don't concentrate on both language on all 4 language skills so that I can manage it.